JP2014180214A - Power conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion system that keeps power supply to a load uninterrupted even if a separate power supply fails.SOLUTION: The power conversion system includes: a plurality of converters C1-C3 connected in parallel between a commercial AC power supply 4 and a load 5; a DC power supply 1 for supplying DC power to the load 5; a current sensor 2 for detecting a current supplied from the plurality of converters C1-C3 and the DC power supply 1 to the load 5; and a control section 3 for selecting the number of converters required to supply the current detected by the current sensor 2 and operating the selected converters. Even if the DC power supply 1 as a separate power supply fails and stops, the converters supply DC power to the load 5.

Description

  The present invention relates to a power conversion system, and particularly to a power conversion system including a plurality of power conversion devices connected in parallel.

  Conventionally, an uninterruptible power supply system in which a load is driven by a plurality of uninterruptible power supply apparatuses connected in parallel is known. In this uninterruptible power supply system, the load current is equally shared by all the uninterruptible power supply devices to drive the load. In this system, even if one uninterruptible power supply fails, the load can be driven by the remaining uninterruptible power supply.

  In another conventional uninterruptible power supply system, the number of operating uninterruptible power supply devices is changed according to the load current (see, for example, Patent Document 1). In this system, the loss which generate | occur | produces in an uninterruptible power supply can be reduced by stopping an unnecessary uninterruptible power supply.

JP-A-3-124228

  By the way, there is a case where it is desired to connect a power source different from the uninterruptible power supply to the load. In this case, when sufficient power is supplied to the load from another power source, the entire uninterruptible power supply is stopped. In this state, if another power supply stops due to failure, there is a problem that the power supply to the load is stopped until the uninterruptible power supply is started.

  Therefore, a main object of the present invention is to provide a power conversion system in which power supply to a load does not stop even when a power supply different from the power conversion apparatus fails.

  The power conversion system according to the present invention is connected in parallel between a first power supply and a load, and each converts the first power supplied from the first power supply into the second power and supplies the second power to the load. A plurality of power conversion devices; a second power source for supplying third power to the load; a current detector for detecting a current supplied to the load from the plurality of power conversion devices and the second power source; and a current detector And a control unit that selects the number of power conversion devices necessary to supply the current detected by the above-described operation, operates each selected power conversion device, and stops each remaining power conversion device. Therefore, even when sufficient power is supplied from the second power source, which is a separate power source, the number of power conversion devices necessary to supply the power is operated. Therefore, even when the separate power supply is stopped due to a failure, the power is immediately supplied to the load from the operating power converter, so that the power supply to the load is not stopped.

  Further, another power conversion system according to the present invention is connected in parallel between a first power supply and a load, and each of the second power is a first power supplied from the first power supply and is a DC power. A plurality of power conversion devices that convert to supply to the load, a second power source that supplies third power to the load, and a DC power that is connected to the load to store and supply a shortage of load current A power storage device, a plurality of power conversion devices and a current detector for detecting a current supplied to the load from the power storage device, a voltage detector for detecting a voltage between terminals of the power storage device, a current detector, and And a control unit that controls the plurality of power conversion devices based on the detection result of the voltage detector. When the voltage between the terminals of the power storage device is higher than a predetermined voltage, the control unit selects the number of power conversion devices necessary for supplying the current detected by the current detector, and selects each selected power conversion device. The power converter is operated and the remaining power converters are stopped. In addition, the control unit supplies the current detected by the current detector and charges the power storage device when the voltage between the terminals of the power storage device is lower than a predetermined voltage. The power converters are selected, the selected power converters are operated, and the remaining power converters are stopped. Therefore, even when another power source connected to the load is stopped due to a failure, the power is immediately supplied from the power storage device to the load, so that the power supply to the load is not stopped.

  Further, another power conversion system according to the present invention is connected in parallel between a first DC power supply and a load, and each of the first DC power supplied from the first DC power supply is supplied to the second DC power supply. A plurality of power converters for converting to power and supplying the load, a power storage device connected to the load for storing DC power and supplying a shortage of load current, and a plurality of power supplies from the first DC power source A current detector for detecting a current supplied to the power conversion device, a voltage detector for detecting a voltage between terminals of the power storage device, and a plurality of power conversion devices based on detection results of the current detector and the voltage detector And a control unit for controlling. When the voltage between the terminals of the power storage device is higher than a predetermined voltage, the control unit selects and selects the number of power conversion devices necessary for power conversion of the current detected by the current detector. Each power converter is operated and the remaining power converters are stopped. In addition, when the voltage between the terminals of the power storage device is lower than a predetermined voltage, the control unit is necessary to convert the current detected by the current detector and charge the power storage device. The number of power converters is selected, each selected power converter is operated, and each remaining power converter is stopped. Therefore, even when another power source connected to the load is stopped due to a failure, the power is immediately supplied from the power storage device to the load, so that the power supply to the load is not stopped.

  As described above, according to the present invention, even when a power supply different from the power conversion device fails, the power supply to the load does not stop.

It is a circuit block diagram which shows the structure of the power conversion system by Embodiment 1 of this invention. It is a circuit block diagram which shows the structure of the control part shown in FIG. It is a figure which shows the table stored in the memory | storage part shown in FIG. It is a time chart which shows the operation | movement of the power conversion system shown in FIG. 3 is a circuit block diagram illustrating a comparative example of the first embodiment. FIG. 5 is a diagram illustrating a modification example of the first embodiment. FIG. FIG. 10 is a circuit block diagram illustrating another modification of the first embodiment. FIG. 10 is a circuit block diagram showing still another modification of the first embodiment. It is a circuit block diagram which shows the structure of the power conversion system by Embodiment 2 of this invention. It is a figure which shows the example of a change of Embodiment 2. FIG. FIG. 10 is a circuit block diagram illustrating another modification of the second embodiment.

[Embodiment 1]
The power conversion system according to the first embodiment of the present invention includes a plurality (three in the figure) of converters C1 to C3, a DC power source 1, a current sensor 2, and a control unit 3, as shown in FIG. Input nodes of converters C1 to C3 are all connected to node N1, and output nodes of converters C1 to C3 are all connected to node N2. Node N1 is connected to commercial AC power supply 4, and node N2 is connected to load 5. Each of converters C1 to C3 converts commercial frequency AC power supplied from commercial AC power supply 4 via node N1 into DC power, and supplies the DC power to load 5 via node N2.

  DC power supply 1 is, for example, a solar battery, is connected to node N2 to generate DC power, and supplies the DC power to load 5 via node N2. Current sensor 2 detects currents supplied from converters C <b> 1 to C <b> 3 and DC power supply 1 to load 5, and provides a signal indicating the detected current value to control unit 3. Based on the output signal of the current sensor 2, the control unit 3 obtains the number of converters (for example, one) required to supply the current detected by the current sensor 2, and the number of converters (for example, C1) Only) and the remaining converters (in this case, C2 and C3) are stopped.

  Moreover, the control part 3 changes the converter to drive | operate with a predetermined period so that the operation time of several converters C1-C3 may become equal. For example, the control unit 3 changes the converter to be operated at a cycle of one day, and operates the three converters C1 to C3 one by one in order. The control unit 3 may be included in each control unit (not shown) of the converters C1 to C3, and the three converters C1 to C3 may be controlled by the control unit 3 of one converter.

  As shown in FIG. 2, the control unit 3 includes comparison circuits 11 and 12, an operation number determination unit 13, a timer 14, a storage unit 15, a failure detection unit 16, and an operation command unit 17. The comparison circuit 11 compares the load current I detected by the current sensor 2 with the threshold current Ith1 corresponding to 33% of the rated current. Output signal φ11 of comparison circuit 11 is set to “L” level when load current I is lower than threshold current Ith1, and is set to “H” level when load current I is higher than threshold current Ith1. The

  The comparison circuit 12 compares the load current I detected by the current sensor 2 with the threshold current Ith2 corresponding to 66% of the rated current. Output signal φ12 of comparison circuit 12 is set to “L” level when load current I is lower than threshold current Ith2, and is set to “H” level when load current I is higher than threshold current Ith2. The

  The number of operating units determining unit 13 determines the number of operating converters based on the output signals φ11 and φ12 of the comparison circuits 11 and 12. When both signals φ11 and φ12 are at “L” level, the load current I is smaller than 33% of the rated current, and therefore the number of operating converters is determined to be one. When the signals φ11 and φ12 are at “H” level and “L” level, respectively, the load current I is larger than 33% and smaller than 66% of the rated current, so the number of operating converters is two. It is determined. When signals φ11 and φ12 are both at “H” level, load current I is larger than 66% of the rated current, and therefore the number of operating converters is determined to be three.

  The timer 14 includes a counter that counts the number of pulses of the clock signal CLK. When the count values of the counter are 0, 1, and 2, the timer 14 outputs signals indicating periods T1, T2, and T3, respectively. If a pulse of the clock signal CLK is input when the count value of the counter is 2, the count value of the counter returns to 0.

  The storage unit 15 stores the table shown in FIG. The top column of the table shows the periods T1, T2, T3, and the second column shows the converter numbers C1, C2, C3 operated in the periods T1, T2, T3 when the number of operating units is one. ing. The third column shows the numbers C2, C3 and C1 of the other converters operated in the periods T1, T2 and T3 when the number of operating units is two, and the fourth column shows the number of operating units 3 The numbers C3, C1, C2 of the other converters operating in the periods T1, T2, T3 in the case of a stand are shown.

  The operation command unit 17 refers to the table stored in the storage unit 15 and operates the number of converters determined by the operation number determination unit 13. That is, when the number of operating units is determined to be 1 by the operating number determining unit 13, the operation command unit 17 operates the converters C1 to C3 in the periods T1 to T3 indicated by the output signal of the timer 14, respectively. In addition, when the number of operating units is determined to be two by the operating unit determining unit 13, the operation command unit 17 converts the converters C1, C2, C2, and C3 in the periods T1, T2, and T3 indicated by the output signal of the timer 14, respectively. , C3 and C1 are operated. In addition, when the operation number determination unit 13 determines that the number of operation units is three, the operation command unit 17 sets the three converters C1 to C3 regardless of the periods T1 to T3 indicated by the output signal of the timer 14. Let it run.

  Further, the operation command unit 17 causes the converter to operate according to the table of FIG. 3 even when the operation number is changed by the operation number determination unit 13 in a certain period. For example, when the number of operating units is changed from three to two in the period T1, the converter C3 among the three converters C1 to C3 that have been operating is stopped. In addition, when the number of operating units is changed from one unit to two units in the period T2, the converter C3 is operated in addition to the operating converter C2.

  Further, failure detection unit 16 detects the presence or absence of each of converters C1 to C3, and provides a signal indicating the detection result to operation command unit 17. For example, when a failure of one converter (for example, C1) is detected by the failure detector 16 and the number of operating units is determined to be 1 by the operating unit determining unit 13, it is determined in advance regardless of the output signal of the timer 14. The remaining two converters (in this case, C2 and C3) are alternately operated at the determined cycle. Further, when a failure of one converter (for example, C1) is detected by the failure detection unit 16 and the number of operating units is determined to be 2 by the operating unit determining unit 13, two units are irrelevant regardless of the output signal of the timer 14. Converters (in this case, C2 and C3) are operated.

  FIG. 4 is a time chart illustrating the operation of the uninterruptible power supply system. At a certain time t0, the operation of the three converters C1 to C3 is started, and the load current I is detected. Load current I is compared with threshold currents Ith1 and Ith2, and the number of converters to be operated is determined based on the comparison result. Here, it is assumed that one is determined.

  At time t1, the count value of the counter in the timer 14 is reset to 0, and a signal indicating the period T1 is output from the timer 14. The operation command unit 17 refers to the table of FIG. 3 to operate only the converter C1 and stops the remaining converters C2 and C3.

  At time t2, the count value of the counter in the timer 14 is incremented (+1) to 1 and a signal indicating the period T2 is output from the timer 14. The operation command unit 17 operates the converter C2 with reference to the table of FIG. 3, and then stops the remaining converters C3 and C1.

  At time t3, the count value of the counter in the timer 14 is incremented (+1) to become 2, and a signal indicating the period T3 is output from the timer 14. The operation command unit 17 operates the converter C3 with reference to the table of FIG. 3, and then stops the remaining converters C1 and C2.

  At time t4, the count value of the counter in the timer 14 is reset to 0, and a signal indicating the period T1 is output from the timer 14. The operation command unit 17 operates the converter C1 with reference to the table of FIG. 3, and then stops the remaining converters C2 and C3.

  Thereafter, it is assumed that the load current I increases and the number of operating units is determined to be 2 by the operating unit determining unit 13. At time t5, the operation command unit 17 refers to the table of FIG. 3 and starts the operation of the converter C2 in addition to the converter C1.

  At time t6, the count value of the counter in the timer 14 is incremented (+1) to become 1, and a signal indicating the period T2 is output from the timer 14. The operation command unit 17 operates the converters C2 and C3 with reference to the table of FIG. 3, and then stops the remaining converter C1.

  At time t7, the count value of the counter in the timer 14 is incremented (+1) to become 2, and a signal indicating the period T3 is output from the timer 14. The operation command unit 17 operates the converters C3 and C1 with reference to the table of FIG. 3, and then stops the remaining converter C2.

  In the first embodiment, even when sufficient power is supplied to the load 5 from the DC power source 1 which is a power source different from the converters C1 to C3, the converters required for supplying the power are operated. The Therefore, even when the DC power source 1 is out of order, power is immediately supplied to the load 5 from the converter in operation, so that the power supply to the load 5 is not stopped.

  Even when the output of the DC power supply 1 fluctuates, the number of converters operated does not change when the load current is constant.

  In addition, the number of converters necessary for supplying the load current among the three converters C1 to C3 is selected, the selected converters are operated, and the remaining converters are stopped. Therefore, compared to the case where all converters C1 to C3 are operated regardless of the load current, the loss generated in converters C1 to C3 can be reduced and the efficiency can be increased.

  Further, the converter to be operated is changed at a predetermined cycle so that the operation times of the three converters C1 to C3 are equal to each other. Therefore, the continuous operation time of each converter can be shortened, and converter failures can be reduced. Moreover, the converter which failed during the stop can be found quickly.

[Comparative example]
FIG. 5 is a circuit block diagram showing a comparative example of the first embodiment, which is compared with FIG. In FIG. 5, this power conversion system is different from the power conversion system of FIG. 1 in that the DC power source 1 is connected to the node N3 on the load 5 side of the current sensor 2 in the wiring between the node N2 and the load 5. It is a point. In this comparative example, when a sufficient current is supplied from the DC power source 1 to the load 5, no current flows from the converters C1 to C3 to the load 5, so the operation of the converters C1 to C3 is stopped. When the DC power source 1 is stopped in failure in this state, no current is supplied to the load 5 until the converters C1 to C3 are activated.

[Modification 1]
In the first embodiment, the case where the three converters C1 to C3 are provided has been described, but the same applies to the case where four or more converters are provided. For example, when four converters C1 to C4 are provided, the timer 14 includes a counter that counts the number of pulses of the clock signal CLK, and when the count value of the counter is 0, 1, 2, 3, respectively, the period T1, A signal indicating T2, T3, T4 is output. If a pulse of the clock signal CLK is input when the count value of the counter is 3, the count value of the counter returns to 0.

  The storage unit 15 stores the table shown in FIG. Periods T1, T2, T3, and T4 are shown in the uppermost column of the table, and converter numbers C1, C2, and C2 that are operated in the periods T1, T2, T3, and T4 when the number of operating units is one are shown in the second column. C3 and C4 are shown. The third column shows the numbers C2, C3, C4 and C1 of the other converters operated at T1, T2, T3 and T4 during the period when the number of operating units is two, and the fourth column Indicates the number C3, C4, C1, C2 of the other converter operated in the period T1, T2, T3, T4 when the number of operating units is 3, and the fifth column shows the number of operating units In this case, the numbers C4, C1, C2, C3 of the other converters operating in the periods T1, T2, T3, T4 are shown.

  Operation command unit 17 operates converters C1 to C4 in periods T1 to T4 indicated by the output signal of timer 14, respectively, when the number of operating units is determined to be one by operating unit determining unit 13. Further, when the number of operating units is determined to be two by the operating unit determining unit 13, the operation command unit 17 converts the converters C1, C2, C2 in the periods T1, T2, T3, T4 indicated by the output signals of the timer 14, respectively. And C3, C3, C4, C4 and C1 are operated.

  Further, when the number of operating units is determined to be 3 by the operating number determining unit 13, the operation command unit 17 converts the converters C1, C2, and C3 in the periods T1, T2, T3, and T4 indicated by the output signals of the timer 14, respectively. , C2, C3, C4, C3, C4, C1, C4, C1, and C2. In addition, when the operation number determination unit 13 determines that the number of operation units is four, the operation command unit 17 sets the four converters C1 to C4 regardless of the periods T1 to T4 indicated by the output signal of the timer 14. Let it run.

  The storage unit 15 also stores a table when one converter has failed. For example, the table of FIG. 3 is stored as a table when the converter C4 has failed. In this case, the timer 14 outputs a signal indicating the periods T1 to T3 instead of the signal indicating the periods T1 to T4, and the same operation as the system illustrated in FIGS. 1 to 4 is performed. Even in the first modification, the same effect as in the first embodiment can be obtained.

[Modification 2]
In the first embodiment, a minimum number of converters are operated to drive the load 5, but in the second modification, a spare converter is operated in addition to that so-called redundant operation. The operation command unit 17 operates the number of converters obtained by adding 1 to the number determined by the operation number determination unit 13. For example, when the load current I is lower than 33% of the rated current, only one converter is operated in the first embodiment, but in this modified example, two converters are operated. In this case, even if one converter suddenly fails during operation, the load 5 can be driven by the other converter. The rotation of the converter to be operated is performed in the same manner as in the first embodiment.

[Modification 3]
FIG. 7 is a circuit block diagram showing a third modification of the first embodiment, which is compared with FIG. In FIG. 7, this power conversion system is different from the power conversion system of FIG. 1 in that the commercial AC power supply 4 is replaced with a DC power supply 6 and the converters C1 to C3 are replaced with DC / DC converters C11 to C13. It is. DC power supply 6 is, for example, a fuel cell, and supplies DC power to DC / DC converters C11 to C13 via node N1. Each of DC / DC converters C11 to C13 converts a DC voltage supplied from DC power supply 6 via node N1 into a predetermined DC voltage, and supplies the DC voltage to load 5 via node N2. The current sensor 2 detects a current supplied to the load 5 from the DC power source 1 and the DC / DC converters C11 to C13, and gives a signal indicating the detected value to the control unit 3.

  The control unit 3 selects the number of DC / DC converters necessary for supplying the current indicated by the signal from the current sensor 2, operates the selected DC / DC converters, and operates the remaining DC / DCs. Stop the converter. Further, the control unit 3 changes the DC / DC converters to be operated at a predetermined cycle so that the operation times of the three DC / DC converters C11 to C13 are equal to each other. Also in this modified example 3, the same effect as in the first embodiment can be obtained.

[Modification 4]
FIG. 8 is a circuit block diagram showing a fourth modification of the first embodiment, which is compared with FIG. In FIG. 8, this power conversion system is different from the power conversion system of FIG. 1 in that converters C1 to C3 are replaced with uninterruptible power supply devices U1 to U3, and DC power supply 1 is replaced with AC power supply 24. is there.

  Each of uninterruptible power supply devices U <b> 1 to U <b> 3 includes a converter 21, a battery 22, and an inverter 23. The input nodes of the three converters 21 are commonly connected to the node N1, and the node N1 is connected to the commercial AC power supply 4. Converter 21 converts commercial AC power from commercial AC power supply 4 into DC power. Battery 22 stores the DC power generated by converter 21. The inverter 23 converts DC power supplied from the converter 21 or the battery 22 into AC power. The output nodes of the three inverters 23 are commonly connected to the node N2.

  When AC power is supplied from the commercial AC power supply 4, DC power generated by the converter 21 is stored in the battery 22 and supplied to the inverter 23, and the AC power generated by the inverter 23 is supplied to the load 5. Is done. When the supply of AC power from the commercial AC power supply 4 is stopped (at the time of a power failure), the converter 21 is stopped, the DC power stored in the battery 22 is supplied to the inverter 23, and the AC power generated by the inverter 23 Is supplied to the load 5. Therefore, the load 5 can be driven even during a power failure during the period in which the DC power is stored in the battery 22.

  The AC power supply 24 is, for example, a generator, is connected to the node N2, generates AC power having a commercial frequency, and supplies the AC power to the load 5. Current sensor 2 detects the current supplied to load 5 from AC power supply 24 and uninterruptible power supply devices U <b> 1 to U <b> 3, and provides a signal indicating the detected value to control unit 3.

  The control unit 3 selects the number of uninterruptible power supply units necessary for supplying the current indicated by the signal from the current sensor 2 and operates each selected uninterruptible power supply unit, and the remaining uninterruptible power supply units. Stop the device. Moreover, the control part 3 changes the uninterruptible power supply unit to operate with a predetermined period so that the operation time of three uninterruptible power supply units may become mutually equal. Also in this modified example 4, the same effect as in the first embodiment can be obtained.

  Needless to say, the first embodiment and the first to fourth modifications may be appropriately combined.

[Embodiment 2]
FIG. 9 is a circuit block diagram showing the configuration of the power conversion system according to the second embodiment of the present invention, which is compared with FIG. 9, this power conversion system is different from the power conversion system of FIG. 1 in that a battery 30 and a voltage sensor 31 are added, and the DC power supply 1 is connected to the current sensor 2 in the wiring between the node N2 and the load 5. Is also connected to the node N3 on the load 5 side.

  The positive electrode of the battery 30 is connected to the node N2, and the negative electrode thereof is grounded. Battery 30 is charged by converters C1 to C3, and supplies a shortage of load current to load 5 via node N2. The voltage sensor 31 detects the voltage of the node N2 (that is, the voltage between the terminals of the battery 30), and gives a signal indicating the detected value to the control unit 3.

  When the voltage between the terminals of the battery 30 detected by the voltage sensor 31 is higher than a predetermined voltage, the control unit 3 selects and selects the number of converters necessary for supplying the current detected by the current sensor 2. Each converter is operated and the remaining converters are stopped.

  In addition, the control unit 3 supplies the current detected by the current sensor 2 and charges the battery 30 when the voltage between the terminals of the battery 30 detected by the voltage sensor 31 is lower than a predetermined voltage. A necessary number of converters are selected, each selected converter is operated, and each remaining converter is stopped. Moreover, the control part 3 changes the converter to drive | operate with a predetermined period so that the operation time of the three converters C1-C3 may become equal mutually.

  Next, the operation of this power conversion system will be described. The rated output voltage of this power conversion system is 100V, and the allowable range of the output voltage is 90 to 110V. It is assumed that the current value detected by the current sensor 2 is 30% of the rated current, and one converter (for example, C1) is in operation. In this state, when the output of the DC power supply 1 decreases and the detection value of the current sensor 2 increases from 30% to 50% of the rated value, the output current of one converter (in this case, C1) is 33 of the rated current. %, 17% of the rated current is discharged from the battery 30 to the load 5.

  When the voltage between the terminals of the battery 30 drops to 92V, another converter (for example, C2) is started, and a total of two converters (in this case, C1 and C2) generate 50% of the rated current. While supplying to the load 5, the battery 30 is charged until the voltage between the terminals of the battery 30 becomes 100V.

  Further, when the output of the DC power supply 1 is recovered and the detection value of the current sensor 2 becomes 30% of the rated current before the voltage between the terminals of the battery 30 decreases to 92V, one converter (in this case) , C1), 30% of the rated current is supplied to the load 5, and 3% of the rated current is supplied to the battery 30 to charge the battery 30.

  In the second embodiment, even when the DC power source 1, which is another power source connected to the load 5, is stopped due to failure, power is immediately supplied from the battery 30 to the load 5, so that the power supply to the load 5 is stopped. There is nothing to do.

  Further, even when the output of the DC power supply 1 decreases and the detection value of the current sensor 2 increases, the other converter is activated only when the voltage between the terminals of the battery 30 decreases below a predetermined voltage. Therefore, even when the output of the DC power supply 1 fluctuates, it is possible to prevent the start and stop of the converter from being repeated frequently. Since other effects are the same as those of the first embodiment, description thereof will not be repeated.

[Modification 1]
FIG. 10 is a circuit block diagram showing a first modification of the second embodiment, which is compared with FIG. 10, this power conversion system is different from the power conversion system of FIG. 9 in that the commercial AC power supply 4 is replaced with a DC power supply 6 and the converters C1 to C3 are replaced with DC / DC converters C11 to C13. It is. The DC power supply 6 supplies DC power to the DC / DC converters C11 to C13 via the node N1. Each of DC / DC converters C11 to C13 converts a DC voltage supplied from DC power supply 6 via node N1 into a predetermined DC voltage, and supplies the DC voltage to load 5 via node N2. The current sensor 2 detects the current supplied from the DC / DC converters C <b> 11 to C <b> 13 to the load 5, and gives a signal indicating the detected value to the control unit 3.

  When the voltage between the terminals of the battery 30 detected by the voltage sensor 31 is higher than the predetermined voltage, the control unit 3 selects the number of DC / DC converters necessary for supplying the current detected by the current sensor 2. Then, the selected DC / DC converters are operated and the remaining DC / DC converters are stopped.

  In addition, the control unit 3 supplies the current detected by the current sensor 2 and charges the battery 30 when the voltage between the terminals of the battery 30 detected by the voltage sensor 31 is lower than a predetermined voltage. A necessary number of DC / DC converters are selected, each selected DC / DC converter is operated, and each remaining DC / DC converter is stopped. Further, the control unit 3 changes the DC / DC converters to be operated at a predetermined cycle so that the operation times of the three DC / DC converters C11 to C13 are equal to each other. Even in the first modification, the same effect as in the second embodiment can be obtained.

[Modification 2]
FIG. 11 is a circuit block diagram showing a second modification of the second embodiment, which is compared with FIG. In FIG. 11, this power conversion system is different from the power conversion system in FIG. 10 in that the current sensor 2 detects a current supplied from the DC power supply 6 to the DC / DC converters C <b> 11 to C <b> 13. The control unit 3 controls the DC / DC converters C11 to C13 based on the detection results of the current sensor 2 and the voltage sensor 31.

  That is, when the voltage between the terminals of the battery 30 is higher than the predetermined voltage, the control unit 3 selects the number of DC / DC converters necessary for power conversion of the current detected by the current sensor 2, and selects each selected The DC / DC converter is operated and the remaining DC / DC converters are stopped. In addition, when the voltage between the terminals of the battery 30 is lower than a predetermined voltage, the control unit 3 converts the current detected by the current sensor 2 into power and charges the battery 30 as many DC / DCs as necessary. A DC converter is selected, each selected DC / DC converter is operated, and each remaining DC / DC converter is stopped. Further, the control unit 3 changes the DC / DC converters to be operated at a predetermined cycle so that the operation times of the three DC / DC converters C11 to C13 are equal to each other.

  Also in this modified example 2, the same effect as in the second embodiment can be obtained. Note that the voltages of the nodes N1 and N2 may be detected, and the DC / DC converters C11 to C13 may be controlled based on the detection result.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1,6 DC power supply, 2 current sensor, 3 control unit, 4 commercial AC power supply, 5 load, C1 to C3, 21 converter, 11, 12 comparison circuit, 13 operation number determination unit, 14 timer, 15 storage unit, 16 failure Detection unit, 17 operation command unit, C11 to C13 DC / DC converter, U1 to U3 uninterruptible power supply, 22, 30 battery, 23 inverter, 24 AC power supply, 31 voltage sensor.

Claims (9)

A plurality of powers connected in parallel between the first power source and the load, each of which converts the first power supplied from the first power source into a second power which is DC power and supplies the second power to the load A conversion device;
A second power source for supplying third power to the load;
A power storage device connected to the load for storing DC power and supplying a shortage of load current;
A current detector for detecting a current supplied to the load from the plurality of power conversion devices and the power storage device;
A voltage detector for detecting a voltage between terminals of the power storage device;
A controller that controls the plurality of power converters based on detection results of the current detector and the voltage detector;
The controller is
When the voltage between the terminals of the power storage device is higher than a predetermined voltage, select the number of power conversion devices necessary to supply the current detected by the current detector, and select each power conversion Operate the device and stop each remaining power converter,
When the voltage between the terminals of the power storage device is lower than the predetermined voltage, the number of power necessary for supplying the current detected by the current detector and charging the power storage device A power conversion system that selects a conversion device, operates each selected power conversion device, and stops each remaining power conversion device. The first power source is an AC power source and the first power is AC power;
The power conversion system according to claim 1, wherein the second power source is a DC power source and the third power is DC power. The first power source is a DC power source and the first power is DC power;
Each power conversion device includes a DC / DC converter that converts an output voltage of the first power source into a predetermined DC voltage,
The power conversion system according to claim 1, wherein the second power source is a DC power source and the third power is DC power. A plurality of electric powers connected in parallel between the first DC power source and the load, each of which converts the first DC power supplied from the first DC power source into second DC power and supplies the second DC power to the load A conversion device;
A power storage device connected to the load for storing DC power and supplying a shortage of load current;
A current detector for detecting a current supplied from the first DC power supply to the plurality of power converters;
A voltage detector for detecting a voltage between terminals of the power storage device;
A controller that controls the plurality of power converters based on detection results of the current detector and the voltage detector;
The controller is
When the voltage between the terminals of the power storage device is higher than a predetermined voltage, select the number of power conversion devices necessary for power conversion of the current detected by the current detector, each selected power Operate the converter and stop each remaining power converter,
When the voltage between the terminals of the power storage device is lower than the predetermined voltage, the number of units necessary to convert the current detected by the current detector and charge the power storage device A power conversion system that selects a power conversion device, operates each selected power conversion device, and stops each remaining power conversion device.   The power conversion system according to claim 4, further comprising a second DC power supply that supplies third DC power to the load.   The power according to any one of claims 1 to 5, wherein the control unit changes the power conversion device to be operated at a predetermined cycle so that the operation times of the plurality of power conversion devices are equal to each other. Conversion system. The controller is
Of the plurality of power conversion devices, exclude the power conversion device in failure from the selection target, select the power conversion device to be operated from a plurality of normal power conversion devices,
The power conversion system according to claim 6, wherein the power conversion devices to be operated are changed at a predetermined cycle so that the operation times of the plurality of normal power conversion devices are equal to each other.   The power conversion system according to claim 6 or 7, wherein the power converter to be operated includes a minimum number of power converters.   The power conversion system according to claim 8, wherein the power conversion device to be operated further includes a spare power conversion device.

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