Power conversion device

Abstract

To provide a power conversion device capable of suppressing an output ripple by making an operation with the appropriate number of parallel devices according to a magnitude of a current rating.SOLUTION: A plurality of power conversion devices 1-N are provided in parallel for a load 200. A series circuit includes: a first current detector HCT_A11, a first reactor L_A11 and an MC 11 for selecting the HCT_A11 having a first current rating sequentially connected in series from the power conversion device to the load; and a second HCT_A21, L_A21 and MC 21 having a small current rating connected in series between both terminals of the MC 11. The same number as the installation number of power conversion devices of series circuits are connected in parallel in each channel connecting each power conversion device with the load. The N number of devices are operated in parallel in a region requiring an operation with the plurality of devices having a large current rating, and the appropriate number of devices are operated in a region having a small current rating according to the current rating.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an operating method for a power conversion device having a plurality of current detectors (hereinafter, also referred to as HCTs) with different ratings for controlling current with high precision, which is connected in parallel. [Background technology]

[0002] There is a demand for power conversion devices with large capacity and multiple current ratings. For this reason, it is necessary to develop a parallel operation method for multiple power conversion devices with multiple current ratings.

[0003] As a prior art technique for operating a power conversion device by switching between a plurality of current detectors with different ratings, for example, the technique described in Patent Document 1 has been proposed.

[0004] FIG. 1 shows an example of the configuration of a power conversion device in the prior art, and shows the configuration described in FIG. 9 of Patent Document 1.

[0005] 1, HCT1 (first current detector) and an electromagnetic contactor (hereinafter also referred to as MC) MC1 for selecting HCT1 are inserted in series in an electric circuit connecting a power converter 100 having an FC (flying capacitor) and a load 200. HCT2 (second current detector) having a different rating from HCT1 and an electromagnetic contactor MC2 for selecting HCT2 are connected in series between both ends of MC1.

[0006] Incidentally, Patent Document 1 does not describe combining outputs of power conversion devices equipped with multiple HCTs with different current ratings to operate multiple devices together.

[0007] FIG. 2 shows a main circuit configuration in the case where a plurality of power conversion devices are operated by directly coupling the outputs of the prior art (the configuration of FIG. 1).

[0008] In FIG. 2, a plurality of power conversion devices 1 and 2 are provided in parallel with a load 200, and in an electric circuit connecting the power conversion device 1 and the load 200, a first electromagnetic contactor MC11, HCT_11, and a reactor L11 that selects a first current detector HCT_11 having a first current rating are connected in series in sequence from the power conversion device 1 to the load 200.

[0009] A second current detector HCT_21 having a second current rating smaller than that of HCT_11 and a second electromagnetic contactor MC21 for selecting HCT_21 are connected in series between both ends of MC11.

[0010] As described above, a first electromagnetic contactor MC12, a first current detector HCT_12, and a reactor L12 are connected in series between the power conversion device 2 and the load 200, and a second current detector HCT_22 and a second electromagnetic contactor MC22 are connected in series between both ends of MC12.

[0011] When power conversion devices are connected in parallel as shown in Figure 2, a current (hereinafter referred to as a cross current) flows between the devices depending on the error in the output voltage. In order to suppress the cross current, reactors L11 and L12 are connected between the devices.

[0012] An example of the control configuration is shown in Figure 3. Power conversion devices 1 and 2 perform current control independently without feeding back the current detection value of the other. In addition, power conversion devices 1 and 2 are configured not to perform carrier synchronization. Current control commands are sent to each power conversion device from the command generation unit. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] JP 2021-180533 A Summary of the Invention [Problem to be solved by the invention]

[0014] Figure 4 shows an example of an output current waveform in response to a current command. Here, a case is shown in which the output MC of power conversion device 1 closes and then the MC of power conversion device 2 closes. There are individual differences in the opening and closing operation of the MC depending on the part. In a large-capacity MC, it may take tens to hundreds of ms from when an opening and closing signal is input until it actually starts operating. Current cannot be output until the MC is closed. This means that the timing at which the output current of each paralleled device rises is different. There is a problem in that it takes a long time for the total output current value to reach the command value.

[0015] Figure 5 shows an example of the steady-state output current and load current waveforms of each power conversion device when carrier synchronization is not implemented. The carrier ripple is shown as a triangular wave. Because carrier synchronization is not implemented between the devices, the carrier ripple may occur equally between the devices. In this case, the carrier ripple of each device is superimposed on the current flowing to the load. Because the carrier ripple of two units occurs in the load current, the carrier ripple is larger than when only one unit is operated.

[0016] The problems with operating multiple units by simply combining the outputs of the conventional technology are summarized below: 1. There is no synchronization configuration for the output current commands between parallel units, resulting in poor response to commands. 2. When multiple units are operated, the output ripple of the power conversion device increases for each unit in parallel. This increases the ripple component of the output current, which increases harmonics and generates unintended losses on the load side. If a small output current is acceptable, the output ripple can be suppressed by operating only one unit. 3. In the case of a configuration with a filter at the output, an output switch may be installed between the load and the filter to separate the load from the circuit. The prior art does not take into consideration a circuit with a current range switching switch and an output switch. For this reason, when current control is performed depending on the opening and closing timing of the current range switching switch and the output switch, the integral term of the current control diverges, causing the current control to become abnormal, resulting in an overcurrent failure, causing the power conversion device to fail and stop, making it impossible to perform the intended control.

[0017] The present invention is devised to solve the above-mentioned problems, and an object of the present invention is to provide a power conversion device that can operate with an appropriate number of parallel units according to the magnitude of the current rating and suppress output ripple. [Means for solving the problem]

[0018] In order to solve the above problem, the power conversion device according to claim 1 is a first current detector having a first current rating, a first reactor, and a first electromagnetic contactor for selecting the first current detector, which are respectively inserted in an electric path connecting each of the power conversion devices and the load and are connected in series from the power conversion device to the load; a second current detector having a second current rating smaller than that of the first current detector, a second reactor, and a second electromagnetic contactor for selecting the second current detector, which are connected in series between both ends of the first electromagnetic contactor; a load connection permission determination processing unit including: a first magnetic contactor side AND circuit which takes a logical AND of a preset opening / closing setting signal of a first magnetic contactor and an operation permission setting signal when the first magnetic contactor is closed; a second magnetic contactor side AND circuit which takes a logical AND of a preset opening / closing setting signal of a second magnetic contactor and an operation permission setting signal when the second magnetic contactor is closed; a first exclusive OR circuit which receives as inputs an output of the first magnetic contactor side AND circuit and an output of the second magnetic contactor side AND circuit; a second exclusive OR circuit which receives as inputs an opening / closing setting signal of the first magnetic contactor and an opening / closing setting signal of the second magnetic contactor; and a load connection permission signal generating AND circuit which takes a logical AND of an output of the first exclusive OR circuit and an output of the second exclusive OR circuit, and outputs a signal which permits load connection when a logical AND condition is established; an opening / closing command / current control permission signal generating unit having: a first magnetic contactor opening / closing command generating AND circuit which takes a logical AND of the load connection permission signal output from the load connection permission determination processing unit and the opening / closing setting signal of the first magnetic contactor to output an opening / closing command for the first magnetic contactor; a second magnetic contactor opening / closing command generating AND circuit which takes a logical AND of the load connection permission signal output from the load connection permission determination processing unit and the opening / closing setting signal of the second magnetic contactor to output an opening / closing command for the second magnetic contactor; and a current control permission signal generating AND circuit which performs a logical OR process on the output of the first magnetic contactor opening / closing command generating AND circuit and the output of the second magnetic contactor opening / closing command generating AND circuit to generate a current control permission signal; a current range switching processing section which has an exclusive OR circuit to which the first electromagnetic contactor opening / closing command signal and the second electromagnetic contactor opening / closing command signal generated by the opening / closing command / current control permission signal generating section are input, and a logical AND circuit which takes a logical AND of an output of the exclusive OR circuit and the second electromagnetic contactor opening / closing command signal, and which selects each current detection value of the first current detector or the second current detector in accordance with an output of the logical AND circuit; The power converter is characterized in that it comprises a current controller which generates a voltage command for a power conversion device by performing proportional control and integral control using set proportional gain and integral gain so that the current detection value selected by the current range switching processing unit becomes the set current command value when the current control permission signal generated by the opening / closing command / current control permission signal generating unit permits control, and which switches the current command and the proportional gain and integral gain to zero when the current control permission signal does not permit control.

[0019] The power conversion device according to claim 2 is the power conversion device according to claim 1, the main circuit of the power conversion device is configured by connecting in parallel a series circuit including the second current detector, the second reactor, and the second electromagnetic contactor between both ends of the first electromagnetic contactor, the number of which corresponds to the number of installed power conversion devices; the second electromagnetic contactor side AND circuit of the load connection permission determination processing unit has AND circuits for taking a logical AND of an open / close setting signal of the second electromagnetic contactor and an operation permission signal when the second electromagnetic contactor is closed, the number of AND circuits being equal to the number of installed power conversion devices; Instead of the first and second exclusive OR circuits and the load connection permission signal generating AND circuit, an operation permission setting side adder that adds up the number of times that each AND result of the first magnetic contactor side AND circuit and the second magnetic contactor side AND for the number of installed power conversion devices is 1, an opening / closing setting side adder that adds up the number of times that the opening / closing setting signal of the first magnetic contactor and the opening / closing setting signal of the second magnetic contactor for the number of installed power conversion devices are closed, a first comparator that outputs 1 only when the addition output of the operation permission setting side adder is equal to 1, a second comparator that outputs 1 only when the addition output of the opening / closing setting side adder is equal to 1, and a load connection permission signal generating AND circuit that takes the AND of the outputs of the first comparator and the second comparator and outputs a signal that permits load connection when a AND condition is established, the second electromagnetic contactor opening / closing command generating AND circuit of the opening / closing command / current control permission signal generating unit has AND circuits which take the logical product of a load connection permission signal and an opening / closing setting signal of the second electromagnetic contactor, the number of which is equal to the number of installed power conversion devices; and the current control permission signal generating OR circuit is composed of OR circuits which perform logical OR processing of an output of the first electromagnetic contactor opening / closing command generating AND circuit and each output of the second electromagnetic contactor opening / closing command generating AND circuit, the number of which is equal to the number of installed power conversion devices; The current range switching processing unit is characterized in that, instead of the exclusive OR circuit, it has an adder that adds up the number of times that the opening / closing command of the first electromagnetic contactor and the opening / closing command of the second electromagnetic contactor, the number of installed power conversion devices, are close commands, and is configured to select each current detection value of the first current detector or the second electromagnetic contactor, the number of installed power conversion devices, depending on the addition result of the adder.

[0020] The power conversion device according to claim 3 comprises: a first current detector having a first current rating, a first reactor, a first electromagnetic contactor for selecting the first current detector, a fourth reactor, and an output side electromagnetic contactor, each of which is inserted in an electric path connecting each of the power converters and the load and connected in series from the power converters to the load; a series circuit consisting of a second current detector having a second current rating smaller than the first current detector, a second reactor, and a second electromagnetic contactor for selecting the second current detector, each of which is connected in parallel to the series circuit of the first reactor and the first electromagnetic contactor; a series circuit consisting of a third current detector having a third current rating smaller than the second current detector, a third reactor, and a third electromagnetic contactor for selecting the third current detector; and an output filter capacitor connected between a common connection point of the series circuit of the first reactor and the first electromagnetic contactor, the fourth reactor, and a negative terminal of the power converters; a first magnetic contactor side AND circuit which takes a logical AND of a preset opening / closing setting signal of the first magnetic contactor and an operation permission setting signal when the first magnetic contactor is closed; a second magnetic contactor side AND circuit which takes a logical AND of a preset opening / closing setting signal of the second magnetic contactor and an operation permission setting signal when the second magnetic contactor is closed; a third magnetic contactor side AND circuit which takes a logical AND of a preset opening / closing setting signal of the third magnetic contactor and an operation permission setting signal when the third magnetic contactor is closed; an operation permission setting side adder which adds a number where each logical AND result of the first to third magnetic contactor side AND circuits is 1; a load connection permission determination processing section including a switching setting side adder that adds a certain number, a first comparator that outputs 1 only when the sum output of the operation permission setting side adder is equal to 1, a second comparator that outputs 1 only when the sum output of the switching setting side adder is equal to 1, a third comparator that outputs 1 when the absolute value of the difference between a voltage detection value that detects the voltage of the output filter capacitor and a voltage detection value that detects the voltage on the load side of the output side electromagnetic contactor is smaller than a set voltage determination level, and a load connection permission signal generating AND circuit that takes a logical AND of the outputs of the first to third comparators and outputs a signal that permits load connection when a logical AND condition is established; a second adder on the operation permission setting side that adds up the numbers of operation permission settings for the first electromagnetic contactor during output filter capacitor voltage control, operation permission settings for the second electromagnetic contactor during output filter capacitor voltage control, and operation permission settings for the third electromagnetic contactor during output filter capacitor voltage control, which are preset and are each permitted; and a fourth comparator that outputs 1 only when the sum output of the second adder on the operation permission setting side is equal to 1; a first AND circuit which takes a logical AND of an open / close setting signal of the first electromagnetic contactor and a load connection permission signal, a second AND circuit which takes a logical AND of an open / close setting signal of the second electromagnetic contactor and a load connection permission signal, and a third AND circuit which takes a logical AND of an open / close setting signal of the third electromagnetic contactor and a load connection permission signal; a fourth AND circuit that takes a logical AND of a signal obtained by logically inverting the load connection permission signal, an output signal of the fourth comparator, and an operation permission signal in the first electromagnetic contactor during output filter capacitor voltage control; a fifth AND circuit that takes a logical AND of a signal obtained by logically inverting the load connection permission signal, an output signal of the fourth comparator, and an operation permission signal in the second electromagnetic contactor during output filter capacitor voltage control; a sixth AND circuit that takes a logical AND of a signal obtained by logically inverting the load connection permission signal, an output signal of the fourth comparator, and an operation permission signal in a third electromagnetic contactor during output filter capacitor voltage control; a first OR circuit that performs a logical OR process on the outputs of the first AND circuit and the fourth AND circuit and outputs an opening / closing command for the first electromagnetic contactor; a second OR circuit that performs a logical OR process on the outputs of the second AND circuit and the fifth AND circuit and outputs an opening / closing command for the second electromagnetic contactor; and a third OR circuit that performs a logical OR process on the outputs of the third AND circuit and the sixth AND circuit and outputs an opening / closing command for the third electromagnetic contactor. a first selection circuit which performs a logical OR operation on the outputs of the first, second and third AND circuits, and outputs 0 when the result is 0 and 1 when the result is 1; and a second selection circuit which performs a logical OR operation on the outputs of the fourth, fifth and sixth AND circuits, and outputs 0 when the result is 0 and 1 when the result is 1; a switching command / current control permission signal generating unit having a current control permission signal generating adder that adds the outputs of the first selection circuit and the second selection circuit and outputs a current control permission signal of either current control non-permission, current control, or output filter capacitor voltage control according to the addition result; a first AND circuit that takes a logical AND of an opening / closing command for the first electromagnetic contactor output from the first OR circuit and an opening / closing state signal for the first electromagnetic contactor; a second AND circuit that takes a logical AND of an opening / closing command for the second electromagnetic contactor output from the second OR circuit and an opening / closing state signal for the second electromagnetic contactor; a third AND circuit that takes a logical AND of an opening / closing command for the third electromagnetic contactor output from the third OR circuit and an opening / closing state signal for the third electromagnetic contactor; an output side electromagnetic contactor opening / closing command generating unit having a first selector that outputs 1 when the load connection permission signal is permission and 0 when the load connection permission signal is not permission, and a fourth AND circuit that takes a logical AND between the output signal of the first selector and a signal resulting from a logical OR process of the outputs of the first to third AND circuits, and outputs an output side electromagnetic contactor opening / closing command; a current range switching processing unit including a second selector that outputs 0 or 1 in response to an opening / closing command for the first electromagnetic contactor, outputs 0 or 2 in response to an opening / closing command for the second electromagnetic contactor, and outputs 0 or 3 in response to an opening / closing command for the third electromagnetic contactor, and an adder that adds up the outputs of the second selector, and that selects one of the current detection values ​​of the first to third current detectors in response to the output of the adder; and a current controller which generates a voltage command for a power conversion device by applying proportional control and integral control using set proportional gain and integral gain so that the current detection value selected by the current range switching processing unit becomes a set current command value when the current control permission signal generated by the opening / closing command / current control permission signal generation unit is current control, and generates a voltage command for a power conversion device by applying proportional control and integral control using set proportional gain and integral gain so that the current detection value selected by the current range switching processing unit becomes a set current command value when the current control permission signal is output filter capacitor voltage control, and switches the current command, and the proportional gain and integral gain to zero when the current control permission signal does not permit current control.

[0021] The power conversion device according to claim 4 comprises: a first current detector on a front side of an output filter having a first current rating, a first reactor, a first electromagnetic contactor on a front side of the output filter for selecting the first current detector, a first electromagnetic contactor on a rear side of the output filter for selecting the first current detector on the rear side of the output filter, a first current detector on a rear side of the output filter having a first current rating, a fourth reactor, and an output side electromagnetic contactor; a series circuit including a second current detector on the front side of the output filter having a second current rating smaller than the first current detector, a second reactor, and a second electromagnetic contactor on the front side of the output filter that selects the second current detector, the series circuits being respectively connected in parallel to the first reactor and the first electromagnetic contactor on the front side of the output filter; and a series circuit including a third current detector on the front side of the output filter having a third current rating smaller than the second current detector, a third reactor, and a third electromagnetic contactor on the front side of the output filter that selects the third current detector. an output filter capacitor connected between a common connection point of the output filter front-side first electromagnetic contactor and the output filter rear-side first electromagnetic contactor and a negative terminal of a power conversion device; a series circuit connected in parallel between both ends of the first electromagnetic contactor on the rear side of the output filter, the series circuit being made up of a second current detector on the rear side of the output filter having a second current rating smaller than the first current detector and a second electromagnetic contactor on the rear side of the output filter selecting the second current detector, and a series circuit being made up of a third current detector on the rear side of the output filter having a third current rating smaller than the second current detector and a third electromagnetic contactor on the rear side of the output filter selecting the third current detector, A load connection permission determination processing unit and an opening / closing command / current control permission signal generating unit as described in claim 3, which changes an opening / closing setting of the first electromagnetic contactor used in the load connection permission determination processing unit to an opening / closing setting of a first electromagnetic contactor on a front side of an output filter and a first electromagnetic contactor on a rear side of the output filter, changes an opening / closing setting of the second electromagnetic contactor to an opening / closing setting of a second electromagnetic contactor on a front side of the output filter and a second electromagnetic contactor on a rear side of the output filter, and changes an opening / closing setting of the third electromagnetic contactor to an opening / closing setting of a third electromagnetic contactor on the front side of the output filter and a third electromagnetic contactor on the rear side of the output filter, changing an operation permission setting signal when the first magnetic contactor is closed to an operation permission setting signal when the first magnetic contactor on the front side of the output filter and the first magnetic contactor on the rear side of the output filter are closed, changing an operation permission setting signal when the second magnetic contactor is closed to an operation permission setting signal when the second magnetic contactor on the front side of the output filter and the second magnetic contactor on the rear side of the output filter are closed, and changing an operation permission setting signal when the third magnetic contactor is closed to an operation permission setting signal when the third magnetic contactor on the front side of the output filter and the third magnetic contactor on the rear side of the output filter are closed, an operation permission setting for the first electromagnetic contactor during the filter capacitor voltage control is changed to an operation permission setting for the first electromagnetic contactor on the front side of the output filter and the first electromagnetic contactor on the rear side of the output filter during the filter capacitor voltage control, an operation permission setting for the second electromagnetic contactor during the filter capacitor voltage control is changed to an operation permission setting for the second electromagnetic contactor on the front side of the output filter and the second electromagnetic contactor on the rear side of the output filter during the filter capacitor voltage control, and an operation permission setting for the third electromagnetic contactor during the filter capacitor voltage control is changed to an operation permission setting for the third electromagnetic contactor on the front side of the output filter and the third electromagnetic contactor on the rear side of the output filter during the filter capacitor voltage control, a load connection permission determination processing unit and a switching command / current control permission signal generating unit configured such that an output of the first logical OR circuit is changed to output an opening / closing command for a first electromagnetic contactor on a front side of an output filter and a first electromagnetic contactor on a rear side of the output filter, an output of the second logical OR circuit is changed to output an opening / closing command for a second electromagnetic contactor on a front side of the output filter and a second electromagnetic contactor on a rear side of the output filter, and an output of the third logical OR circuit is changed to output an opening / closing command for a third electromagnetic contactor on a front side of the output filter and a third electromagnetic contactor on a rear side of the output filter; The output side electromagnetic contactor opening / closing command generating unit according to claim 3 changes the opening / closing command of the first electromagnetic contactor used in the output side electromagnetic contactor opening / closing command generating unit to an opening / closing command of an output filter front side first electromagnetic contactor and an output filter rear side first electromagnetic contactor, and changes a status signal of the first electromagnetic contactor to a status signal of the output filter front side first electromagnetic contactor and the output filter rear side first electromagnetic contactor; changing the opening / closing command of the second electromagnetic contactor to an opening / closing command of the second electromagnetic contactor on the front side of the output filter and the second electromagnetic contactor on the rear side of the output filter, and changing the status signal of the second electromagnetic contactor to a status signal of the second electromagnetic contactor on the front side of the output filter and the second electromagnetic contactor on the rear side of the output filter; an output side electromagnetic contactor opening / closing command generating unit configured to change the opening / closing command of the third electromagnetic contactor to an opening / closing command of the third electromagnetic contactor on the front side of the output filter and the third electromagnetic contactor on the rear side of the output filter, and to change a status signal of the third electromagnetic contactor to a status signal of the third electromagnetic contactor on the front side of the output filter and the third electromagnetic contactor on the rear side of the output filter; a current range switching processing unit including: a second selector that outputs 0 or 1 in response to an opening / closing command for a first electromagnetic contactor on the front side of the output filter and a first electromagnetic contactor on the rear side of the output filter, that outputs 0 or 2 in response to an opening / closing command for a second electromagnetic contactor on the front side of the output filter and a second electromagnetic contactor on the rear side of the output filter, and that outputs 0 or 3 in response to an opening / closing command for a third electromagnetic contactor on the front side of the output filter and a third electromagnetic contactor on the rear side of the output filter; an adder that adds up outputs of the second selector; an output filter front-side selector that selects a current detection value of one of the first to third current detectors on the front side of the output filter in response to an output of the adder; and an output filter rear-side selector that selects a current detection value of one of the first to third current detectors on the rear side of the output filter in response to an output of the adder; When the current control permission signal generated by the switching command / current control permission signal generation unit is current control, proportional control is performed using a set proportional gain for current control so that the current detection value of the output filter front-side current detector selected by the output filter front-side selector becomes the set current command value; generating a voltage command for the power conversion device by performing integral control using an integral gain for current control that is set so that the current detection value of the output filter rear side current detector becomes a set current command value; The power conversion device is characterized in that, when the current control permission signal is output filter capacitor voltage control, a voltage command for the power conversion device is generated by performing proportional control and integral control using a proportional gain and an integral gain for the set output filter capacitor voltage control so that the current detection value of the output filter front-side current detector selected by the output filter front-side selector becomes a current command value during the set output filter capacitor voltage control, and, when the current control permission signal is current control disallowance, the current controller switches the current command, the proportional gain, and the integral gain to zero.

[0022] The power conversion device according to claim 5 is the power conversion device according to claim 4, When a current control permission signal specifying current control is output from the opening / closing command / current control permission signal generating unit, the current control device is characterized in that it is provided with a current command enable / disable selection circuit which enables the current command on the input side of the current controller only when the states of the output side electromagnetic contactors connected to the main circuits of all power conversion devices connected in parallel are all closed.

[0023] The power conversion device according to claim 6 is the power conversion device according to claim 4 or 5, The power conversion device is characterized in that an operation permission setting determination unit is provided in accordance with the number of power conversion devices operating in parallel, and the operation permission setting determination unit is selected in accordance with the set number of parallel operation units, the operation permission setting determination unit counts the number of opening and closing of each electromagnetic contactor based on status signals of the first electromagnetic contactor on the front side of the output filter and the first electromagnetic contactor on the rear side of the output filter, status signals of the second electromagnetic contactor on the front side of the output filter and the second electromagnetic contactor on the rear side of the output filter, and status signals of the third electromagnetic contactor on the front side of the output filter and the third electromagnetic contactor on the rear side of the output filter. The operation permission setting determination unit determines the operation permission setting with the electromagnetic contactor closed for the electromagnetic contactor with the smallest number of opening and closing.

[0024] The power conversion device according to claim 7 is the power conversion device according to claim 4 or 5, The present invention is characterized in that a circuit between any one of the multiple power conversion devices and a load is enabled, and for the circuits between the other power conversion devices and the load, the second current detector, the second reactor, the second electromagnetic contactor, the third current detector, the third reactor, and the third electromagnetic contactor are deleted, the current range switching processing unit is deleted, the feedback input to the current controller is only the current detection value of the first current detector, and the setting to permit operation with the second electromagnetic contactor on the front side and the second electromagnetic contactor on the rear side of the output filter closed and the setting to permit operation with the third electromagnetic contactor on the front side and the third electromagnetic contactor on the rear side of the output filter closed are not permitted.

[0025] The power conversion device according to claim 8 is the power conversion device according to claim 4 or 5, a first carrier frequency selection unit which compares a rated current of the power conversion device with a rated current when the front-side first electromagnetic contactor and the rear-side first electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the first electromagnetic contactor is selected with a current obtained by dividing the rated current of the power conversion device by a first set number with the rated current when the front-side first electromagnetic contactor and the rear-side first electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the first electromagnetic contactor is selected with a current obtained by dividing the rated current of the power conversion device by a second set number with the rated current when the front-side first electromagnetic contactor and the rear-side first electromagnetic contactor of the output filter are selected, and selects one of first to third carrier frequencies which are set to be successively higher according to a total value of the comparison results in which the rated current is smaller when the first electromagnetic contactor is selected; a second carrier frequency selection unit which compares a rated current of the power conversion device with a rated current when the front-side second electromagnetic contactor and the rear-side second electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the second electromagnetic contactor is selected with a current obtained by dividing the rated current of the power conversion device by a first set number with the rated current when the front-side second electromagnetic contactor and the rear-side second electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the second electromagnetic contactor is selected with a current obtained by dividing the rated current of the power conversion device by a second set number with the rated current when the front-side second electromagnetic contactor and the rear-side second electromagnetic contactor of the output filter are selected, and selects one of first to third carrier frequencies which are set to be successively higher according to a total value of the comparison results in which the rated current is smaller when the second electromagnetic contactor is selected; a third carrier frequency selection unit which compares a rated current of the power conversion device with a rated current when the front third electromagnetic contactor and the rear third electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the third electromagnetic contactor is selected with a current obtained by dividing the rated current of the power conversion device by a first set number with a rated current when the front third electromagnetic contactor and the rear third electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the third electromagnetic contactor is selected with a current obtained by dividing the rated current of the power conversion device by a second set number with the rated current when the front third electromagnetic contactor and the rear third electromagnetic contactor of the output filter are selected, and selects one of the first to third carrier frequencies having frequencies set successively higher according to a total value of the comparison results in which the rated current is smaller when the third electromagnetic contactor is selected; a carrier frequency setting unit that sets the output of the first carrier frequency selection unit when the first electromagnetic contactor on the front side of the output filter and the first electromagnetic contactor on the rear side of the output filter are selected, that sets the output of the second carrier frequency selection unit when the second electromagnetic contactor on the front side of the output filter and the second electromagnetic contactor on the rear side of the output filter are selected, and that sets the output of the third carrier frequency selection unit when the third electromagnetic contactor on the front side of the output filter and the third electromagnetic contactor on the rear side of the output filter are selected. Effect of the Invention

[0026] (1) According to the invention described in claims 1 to 8, in an area where multiple units with a large current rating are required to be operated, multiple units can be operated in parallel, and in an operating area where the operable current is small, an appropriate number of units can be operated according to the current rating. This reduces the carrier ripple, thereby reducing harmonics caused by the carrier. (2) According to the invention recited in claim 3, in a device having a filter capacitor on the output side of a power conversion device, the same effect as that of (1) above can be obtained. (3) According to the invention described in claim 4, in a device in which a filter capacitor is provided on the output side of a power conversion device and reactors are provided in front of and behind the filter capacitor to form an LCL type filter, an effect similar to that of (1) can be obtained. (4) According to the invention described in claim 5, in a case where the response speed is defined as the time from when a command value changes until the output current reaches a target current, the response speed of the output current is It can be expedited. (5) According to the invention as set forth in claim 6, the number of times each electromagnetic contactor is opened and closed is determined, and the number of times each electromagnetic contactor is opened and closed can be made uniform, so that the life of the device can be expected to be extended. (6) According to the invention described in claim 7, it is possible to reduce the number of parts by deleting unnecessary circuits, thereby reducing costs and panel size. (7) According to the invention described in claim 8, it is possible to change the carrier frequency without generating current pulsation in the load, and it is possible to reduce carrier ripple without increasing the harmonics or carrier frequency caused by a sudden change in current. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a configuration diagram showing an example of a power conversion device including multiple HCTs with different current ratings according to the prior art. [Diagram 2] FIG. 1 is a configuration diagram showing a case where outputs of power conversion devices according to the prior art are combined to operate a plurality of power conversion devices. [Diagram 3] FIG. 13 is a control configuration diagram when prior art is combined. [Figure 4] FIG. 4 is an output current waveform diagram for a current command in the control of FIG. 3. [Diagram 5] FIG. 4 is a current waveform diagram of each part in the control of FIG. 3. [Figure 6] 1 is a main circuit configuration diagram of a power conversion device according to a first embodiment of the present invention. [Figure 7] FIG. 2 is a diagram showing an HCT selection MC opening and closing control configuration in the first embodiment of the present invention. [Figure 8] FIG. 2 is a basic control configuration diagram of the power conversion device according to the first embodiment of the present invention. [Figure 9] FIG. 6 is a main circuit configuration diagram of a power conversion device according to a second embodiment of the present invention. [Figure 10] FIG. 11 is a diagram showing an HCT selection MC opening and closing control configuration according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a basic control configuration diagram of a power conversion device according to a second embodiment of the present invention. [Figure 12] 11 is a main circuit configuration diagram of a power conversion device according to a third embodiment of the present invention. [Figure 13] FIG. 11 is a diagram showing an HCT selection MC opening and closing control configuration according to a third embodiment of the present invention. [Figure 14] FIG. 11 is a diagram showing an output MC switching control configuration according to a third embodiment of the present invention. [Figure 15] FIG. 11 is a basic control configuration diagram of a power conversion device according to a third embodiment of the present invention. [Figure 16] FIG. 11 is a main circuit configuration diagram of a power conversion device according to a fourth embodiment of the present invention. [Figure 17] FIG. 13 is a diagram showing an HCT selection MC opening and closing control configuration in the fourth embodiment of the present invention. [Figure 18] FIG. 11 is a diagram showing an output MC switching control configuration according to a fourth embodiment of the present invention. [Figure 19] FIG. 11 is a basic control configuration diagram of a power conversion device according to a fourth embodiment of the present invention. [Figure 20] FIG. 11 is a basic control configuration diagram of a power conversion device according to a fifth embodiment of the present invention. [Figure 21] FIG. 13 is an output current waveform diagram when a current command is received and current control is performed before all output MCs are turned on. [Figure 22] FIG. 13 is an output current waveform diagram when the control according to the fifth embodiment of the present invention is carried out. [Figure 23] FIG. 23 is a configuration diagram of each MC opening and closing count processing in the sixth embodiment of the present invention. [Figure 24] FIG. 23 is a configuration diagram showing operation permission setting with each MC closed in the sixth embodiment of the present invention. [Diagram 25] FIG. 23 is a configuration diagram showing operation permission setting when the number of parallel units is 1 in the sixth embodiment of the present invention. [Figure 26] FIG. 23 is a configuration diagram showing operation permission setting for a parallel operation of two units according to a sixth embodiment of the present invention. [Figure 27] FIG. 23 is a configuration diagram showing operation permission setting for a parallel operation of three units according to a sixth embodiment of the present invention. [Figure 28] FIG. 13 is a main circuit configuration diagram of a power conversion device according to a seventh embodiment of the present invention. [Figure 29]FIG. 13 is a configuration diagram of carrier frequency selection when a first electromagnetic contactor is selected in the eighth embodiment of the present invention. [Diagram 30] FIG. 13 is a diagram showing a carrier frequency setting configuration according to an eighth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiment. As a prerequisite for the present invention, the following circuit configuration will be described.

[0029] 1. Carrier synchronization is not performed between paralleled power conversion devices. 2. The power conversion device is not limited to one having a flying capacitor. Under the prerequisites shown above, it is necessary to develop a parallel operation method for multiple power conversion devices with multiple current ratings while achieving a parallel operation method, improving control accuracy, and preventing an increase in carrier ripple. EXAMPLES

[0030] FIG. 6 shows a main circuit configuration of the power conversion device in the first embodiment.

[0031] In Figure 6, multiple power conversion devices 1 and 2 are provided in parallel with a load 200, and in an electric circuit connecting the power conversion device 1 and the load 200, a first current detector HCT_A11 having a first current rating, a first reactor L_A11 having a first inductance value, and a first electromagnetic contactor MC11 that selects the first current detector HCT_A11 are connected in series in this order from the power conversion device 1 to the load 200.

[0032] A series circuit consisting of a second current detector HCT_A21 having a second current rating smaller than that of HCT_A11, a second reactor L_A21 having a second inductance value, and a second electromagnetic contactor MC21 that selects HCT_A21 is connected in parallel across the first electromagnetic contactor MC11.

[0033] The main circuit of the electric path connecting the power conversion device 2 and the load 200 is configured in the same manner as above, with the suffixes of HCT_A, L_A, and MC changed from "1" to "2." In this embodiment, HCT_A11 and HCT_A12 are used when operating with a large current rating, and HCT_A21 and HCT_A22 are used when operating with a small current rating. The opening and closing of MC and the selection of HCT are defined in Table 1.

[0034] [Table 1]

[0035] Table 1 shows the case of power conversion device 1, but the case of power conversion device 2 is the same except that the subscript is changed to 2.

[0036] Figure 7 shows the HCT selection MC switching control configuration diagram. Reference numeral 10 denotes a load connection permission determination processing unit, and 20 denotes a switching command / current control permission signal generation unit. Reference numeral 11 denotes a first magnetic contactor side logical product circuit that takes the logical product of a preset switching setting signal of the first magnetic contactor MC11 and an operation permission setting signal when the first magnetic contactor MC11 is closed. Reference numeral 12 denotes a second magnetic contactor side logical product circuit that takes the logical product of a preset switching setting signal of the second magnetic contactor MC21 and an operation permission setting signal when the second magnetic contactor MC21 is closed.

[0037] Reference numeral 13 denotes a first exclusive-OR circuit having as input the output of the first electromagnetic contactor side AND circuit 11 and the output of the second electromagnetic contactor side AND circuit 12, and reference numeral 14 denotes a second exclusive-OR circuit having as input the opening / closing setting signal of the first electromagnetic contactor MC11 and the opening / closing setting signal of the second electromagnetic contactor MC21.

[0038] Numeral 15 denotes a logical AND circuit for generating a load connection permission signal, which takes the logical AND of the output of the first exclusive OR circuit 13 and the output of the second exclusive OR circuit 14, and outputs a signal (permitted 1; not permitted; 0) that permits load connection when the logical AND condition is satisfied.

[0039] Reference numeral 16 denotes a logical AND circuit for generating a first electromagnetic contactor opening / closing command, which takes the logical AND of the load connection permission signal output from the load connection permission determination processing unit 10 and the opening / closing setting signal of the first electromagnetic contactor MC11, and outputs an opening / closing command for the first electromagnetic contactor MC11.

[0040] Reference numeral 17 denotes a second electromagnetic contactor open / close command generating logical product circuit which takes the logical product of the load connection permission signal output from the load connection permission determination processing unit 10 and the open / close setting signal of the second electromagnetic contactor MC21 and outputs an open / close command for the second electromagnetic contactor MC21.

[0041] Reference numeral 18 denotes a logical AND circuit for generating a current control permission signal, which performs a logical OR operation on the output of the logical AND circuit 16 for generating the first electromagnetic contactor opening / closing command and the output of the logical AND circuit 17 for generating the second electromagnetic contactor opening / closing command, and generates a current control permission signal.

[0042] 8 shows a basic control configuration diagram of the power conversion device in Example 1. Here, one power conversion device is shown, and the other power conversion devices have the same configuration.

[0043] In Fig. 8, 30 is a current range switching processing unit, which is configured as follows. It has an exclusive OR circuit 31 to which the MC11 opening / closing command signal and the MC21 close command signal generated by the opening / closing command / current control permission signal generating unit 20 are input, and a logical AND circuit 32 which takes the logical AND of the output of the exclusive OR circuit 31 and the MC21 opening / closing command signal, and selects each current detection value of the first current detector HCT_A11 or the second current detector HCT_A21 according to the output of the logical AND circuit 32 (0: MC11 closed, 1: MC21 closed). The output current of the current range switching processing unit 30 is used as a feedback signal for a current controller 40.

[0044] Reference numeral 41 denotes a selector which selects a current command 1 when the current control permission signal output from the logical OR circuit 18 for generating the current control permission signal of the opening / closing command / current control permission signal generating unit 20 indicates control permission 1, and selects 0 when the current control permission signal is output from the logical OR circuit 18 for generating the current control permission signal of the opening / closing command / current control permission signal generating unit 20 indicates control permission 0.

[0045] When the current control permission signal indicates control permission, the current controller 40 performs proportional control and integral control using the set proportional gain Kp and integral gain Ki so that the current detection value selected by the current range switching processing unit 30 becomes the set current command value, thereby generating a voltage command for the power conversion device, and when the current control permission signal indicates control prohibition, the current command, the proportional gain, and the integral gain are switched to zero. 42 indicates a delay unit, and 43 indicates a limiter.

[0046] The current controller is configured with integral processing like a PI controller. In terms of the current control configuration, when the current control permission signal is 0, the current command and proportional gain of the current control are set to 0. The integral term also has an initial integral term value set. Here, the proportional gain is set to 0, but there is no problem if the integral gain is also set to 0. The current detection value is determined by current range switching processing. The current detection value is configured to switch to an appropriate detection value depending on the selected MC opening and closing command.

[0047] Table 2 shows the truth table for the HCT selection MC opening and closing control.

[0048] [Table 2]

[0049] According to Table 2, it can be seen that the load connection permission signal, the relevant MC opening and closing command, and the current control permission signal will be 1 only when the opening and closing settings of the MC for which operation permission is set and the relevant MC are 1. If the opening and closing settings of MC11 and MC21 are both 1, it can be seen that the load connection permission signal, each MC opening and closing command, and the current control permission signal will be 0. It is possible to give opening and closing commands to the intended MC with HCT selection MC opening and closing control. Furthermore, even if the opening and closing settings are 1 for both MCs, the MC opening and closing command will be 0, so no malfunction will occur. The effect and operation of the control configuration will be explained below.

[0050] The current range switching processing unit 30 will now be described. Table 3 shows a truth table for the current range switching processing.

[0051] [Table 3]

[0052] By performing this process, it becomes possible to appropriately select the relationship between HCT and MC selection. Also, when there is no selection, or when MC11 and MC21 are selected, HCT_A11 is selected. This is set to prevent malfunction because, regardless of whether MC11 or MC21 is open, HCT_A11 always detects current due to the configuration. When switching MCs or operating with an MC that is not permitted to operate, both MC11 and MC21 may be in the open state.

[0053] When both MC11 and MC21 are open, the current detection value is 0. For this reason, if a current command is given and the integral term of the current control is operating, the deviation that occurs is integrated by the integral term, resulting in an abnormal value and causing the current control to become abnormal. As a result, an overcurrent fault occurs and the device breaks down. When the current control permission signal is 0, the current command and current control proportional gain are set to 0 and the integral term initial value is set to the integral term, stopping the integral action. When both MC11 and MC21 are open, the integral term stops and the current control does not become abnormal. When the MC you want to operate is commanded to close, the current control permission signal is 1, causing the current control to operate normally.

[0054] For example, power conversion device 1 is set to permit operation with MC11 and MC21, and power conversion device 2 is set to permit operation with MC12, but not with MC22. In this case, since each control operates as described above, when the current rating is large, operation is possible with both power conversion devices 1 and 2, and when the current rating is small, operation is possible with only power conversion device 1.

[0055] As described above, according to the first embodiment, in an area where multiple units with large current ratings are required to operate, two units can be operated in parallel. In an operating area where the current rating of one unit is small, operation with one unit is possible. This reduces the carrier ripple, and therefore the harmonics caused by the carrier can be reduced. EXAMPLES

[0056] Fig. 9 shows a basic circuit configuration diagram of a power conversion device in Example 2. The difference between Fig. 9 and Fig. 6 of Example 1 is that N power conversion devices 1 to N are provided for a load 200, and series circuits each consisting of a second current detector HCT_A21, a second reactor L_A21, and a second electromagnetic contactor MC21, which are connected in parallel between both ends of the first electromagnetic contactor MC11, are connected in parallel by the number of the installed power conversion devices, and other parts are configured in the same manner as in Fig. 6.

[0057] In this embodiment, when operating with a large current rating, HCT_A11, HCT_A12, ···HCT1N are used, and when operating with a small current rating, HCT_AN1, HCT_AN2, ···HCTNN are used. The opening and closing of MC and the selection of HCT are defined in Table 4.

[0058] [Table 4]

[0059] Table 4 shows the case of power conversion device 1, but it is the same for power conversion device 2 just by changing the subscript to 2, and for power conversion device N just by changing the subscript to N. Figure 10 shows the HCT selection MC switching control configuration diagram.

[0060] 10, the load connection permission determination processing unit 50 in the second embodiment is configured as follows. 51a is a logical product circuit that takes the logical product of a preset opening / closing setting signal of the electromagnetic contactor MC11 and an operation permission setting signal with MC11 closed. 51b is a logical product circuit that takes the logical product of a preset opening / closing setting signal of MC21 and an operation permission setting signal with MC21 closed. N logical product circuits 51 are similarly provided, and 51n is a logical product circuit that takes the logical product of a preset opening / closing setting signal of MCN1 and an operation permission setting signal with MCN1 closed.

[0061] Reference numerals 52a to 52n denote selectors that select 0 when the output of each of the AND circuits 51a to 51n is 0 and select 1 when the output is 1, and reference numeral 53 denotes an operation permission setting side adder that adds a number that is 1 as the selection result of the selectors 52a to 52n.

[0062] Reference numeral 54a denotes a selector which selects 0 when the switching setting signal of MC11 is 0 and 1 when it is 1, and reference numeral 54b denotes a selector which selects 0 when the switching setting signal of MC21 is 0 and 1 when it is 1. Similarly, N sets of selectors 54 are provided, and reference numeral 54n denotes a selector which selects 0 when the switching setting signal of MCN1 is 0 and 1 when it is 1.

[0063] Reference numeral 55 denotes an open / close setting side adder that adds the number that is 1 as a result of the selection by the selectors 54a to 54n.

[0064] Reference numeral 56 denotes a comparator which outputs 1 only when the sum output of the operation permission setting side adder 53 is equal to 1; and reference numeral 57 denotes a comparator which outputs 1 only when the sum output of the open / close setting side adder 55 is equal to 1.

[0065] Reference numeral 58 denotes a logical AND circuit for generating a load connection permission signal that takes the logical AND of the outputs of the comparators 56 and 57, and outputs a load connection permission signal that specifies permission 1 when the logical AND condition is satisfied and specifies non-permission 0 when the logical AND condition is not satisfied.

[0066] A logical AND circuit 59a takes a logical AND of the load connection permission signal and the MC11 switching setting signal to output an MC11 switching command signal. A logical AND circuit 59b takes a logical AND of the load connection permission signal and the MC21 switching setting signal to output an MC21 switching command signal.

[0067] Similarly, N logical product circuits 59 are provided, and 59n is a logical product circuit which takes the logical product of the load connection permission signal and the MCN1 switching setting signal and outputs an MCN1 switching command signal.

[0068] Reference numeral 60 denotes a logical sum circuit for generating a current control permission signal, which performs a logical sum process on the outputs of the logical sum circuits 59a to 59n and outputs a current control permission signal.

[0069] The AND circuits 59a to 59n and the OR circuit 60 constitute a switching command / current control permission signal generating unit 61.

[0070] In FIG. 10, the load connection permission determination process includes the following processes. (1) The logical product of the open / closed setting of each MC and the closed operation permission setting is taken (51a to 51n). If the result of the logical product is 0, 0 is output, and if it is 1, 1 is output. The outputs for all MCs are added, and the result is compared with 1. If they are equal, 1 is output, and if they are not equal, 0 is output. (2) When the MC open / close setting is 0, 0 is output, and when it is 1, 1 is output. The results for all MCs are added (55), the result is compared with 1, and if they are equal, 1 is output, and if they are not equal, 0 is output. (3) The logical product of the results of (1) and (2) is taken to generate a load connection permission signal (58). The logical product of the load connection permission signal and the MC switching settings is taken to generate each MC switching command (59a to 59n). The logical sum of these MC switching commands is configured to generate a current control permission signal (60).

[0071] 11 shows a basic control configuration diagram in the second embodiment. The current range switching processing unit 70 in the second embodiment is configured as follows: 71a is a selector which selects 0 when the opening / closing command of the first electromagnetic contactor MC11 is 0 and 1 when it is 1 (close command), 71b is a selector which selects 0 when the opening / closing command of the second electromagnetic contactor MC21 is 0 and 2 when it is 1 (close command), N selectors 71 are provided, and 71n is a selector which selects 0 when the opening / closing command of the Nth electromagnetic contactor MCN1 is 0 and N when it is 1 (close command).

[0072] Reference numeral 72 denotes an adder that adds the outputs of the selectors 71a to 71n (adds the number that is a close command). Reference numeral 73 denotes a current detection value setter that sets one of the current detection value of the first current detector HCT_A11, the current detection value of the second current detector HCT_A21, ..., the current detection value of HCT_AN1 according to the output of the adder 72.

[0073] The current controller 40 and the circuit on the input side thereof in the second embodiment are configured in the same manner as in FIG. 8 of the first embodiment.

[0074] FIG. 11 shows one power conversion device. Other power conversion devices may have a similar configuration. The current controller 40 is configured with integral processing like a PI controller. As a current control configuration, when the current control permission signal is 0, the proportional gain of the current command and current control is set to 0. The integral term also sets an initial value. Here, the proportional gain is set to 0, but there is no problem if the integral gain is also set to 0.

[0075] The current range switching processing unit 70 determines the current detection value. A number corresponding to the MC opening and closing command is output, and the current detection value of the HCT is appropriately set by setting the corresponding number. For example, if the MC11 opening and closing command is 1, 1 is output; if the MC21 opening and closing command is 1, 2 is output; if the MCN1 opening and closing command is 1, N is output. The output results are added by an adder 72. If the sum result is 1, the current detection value of HCT_A11 is set; if it is 2, the current detection value of HCT_A21 is set; and if it is N, the current detection value of HCT_AN1 is set.

[0076] Tables 5, 6, and 7 show truth tables for the load permitted connection determination process in the second embodiment.

[0077] [Table 5]

[0078] [Table 6]

[0079] [Table 7]

[0080] It can be seen that the load connection permission signal will be 1 only when the MC for which operation permission is set and the switching setting of the corresponding MC are 1. It can also be seen that the load connection permission signal will be 0 even if multiple MC switching settings are 1.

[0081] Moreover, the switching command of each MC is the logical product of each MC switching setting and the load connection permission signal. It is clear from Table 5 that the MC switching command is 0 or 1 appropriately according to the operation permission setting and the MC switching setting. Since the current control permission signal performs logical OR processing of each MC switching command, it is also clear that it is a signal that becomes 1 only when any of the MC switching commands becomes 1. Other parts are configured in the same way as in Example 1.

[0082] The action and operation of the control configuration will be explained below. The current range switching process will be described. As mentioned above, one of the MC switching command signals will be 1. An appropriate number is selected according to this MC switching command, and the current detection value is selected accordingly. For example, if the MC11 switching command is 1, 1 is selected and the current detection value of HCT_A11 is selected. Similarly, if the MC21 switching command is 1, 2 is selected and the current detection value of HCT_A21 is selected, and if the MCN1 switching command is 1, N is selected and the current detection value of HCT_AN1 is selected.

[0083] As in the first embodiment, when the current control permission signal is 0, the integral action is stopped by setting the current command, current control proportional gain, and integral term initial value to the integral term. When the MC to be operated is in a close command, the current control permission signal becomes 1, and the current control operates normally.

[0084] For example, power conversion device 1 is set to permit operation with MC11, MC21, and MCN1, power conversion device 2 is set to permit operation with MC12 and MC22, and power conversion device N is set to permit operation with MCN1. In this case, since each control operates as described above, when the current rating is large, operation is performed with power conversion devices 1, 2, and N, when the current rating is the next smallest, operation is performed with power conversion devices 1 and 2, and when the current rating is the smallest, operation is possible with only power conversion device 1.

[0085] As described above, according to the second embodiment, since the configuration is applicable not only to two-unit parallel connection but also to multiple-unit parallel connection from 2 to N units, in an area where multiple units with a large current rating are required to be operated, it is possible to operate N units in parallel. In an operating area where the operable current is small according to each current rating, it is possible to operate an appropriate number of units, so that the carrier ripple is reduced and the harmonics caused by the carrier can be reduced. EXAMPLES

[0086] FIG. 12 shows a main circuit configuration diagram of a power conversion device in Example 3. In Example 3, since the current rating is three, the number of HCTs and MCs per unit is three. The number of parallel power conversion devices is three. However, as in Example 2, the number of HCTs and MCs per unit and the number of parallel power conversion devices can be up to N. The main circuit configuration of this example is intended to have a capacitor at the output. In this example, the output filter is in the form of an LCL. Also, a switch for isolating the load is provided after the L in the final stage of the LCL.

[0087] In FIG. 12, three power conversion devices 1, 2, and 3 are provided for a load 200, and in an electric circuit connecting the power conversion device 1 and the load 200, a first current detector HCT_A11 having a first current rating, a first reactor L_A11, a first electromagnetic contactor MC_A11, a fourth reactor L_B11, and an output side electromagnetic contactor MC_C11 for disconnecting the load are connected in series from the power conversion device 1 to the load 200.

[0088] Between the common connection point of MC_A11 and L_B11 and the negative electrode side of the power conversion device 1, an output filter capacitor C11 is connected.

[0089] The series circuit of L_A11 and MC_A11 is connected in parallel with a series circuit consisting of a second current detector HCT_A21 having a second current rating smaller than that of HCT_A11, a second reactor L_A21, and a second electromagnetic contactor MC_A21 that selects HCT_A21, and a series circuit consisting of a third current detector HCT_A31 having a third current rating smaller than that of HCT_A21, a third reactor L_A31, and a third electromagnetic contactor MC_A31 that selects HCT_A31.

[0090] The main circuits between the power converters 2, 3 and the loads are configured in the same manner as above, with the suffixes at the end of each part being changed from 1 to 2, 3, respectively.

[0091] In FIG. 13, reference numeral 80 denotes a load connection permission determination processing unit that determines whether to permit or not permit a load connection, and is configured as follows.

[0092] Reference numeral 81 denotes a logical AND circuit which takes the logical AND of a preset open / close setting signal for MC_A11 and a setting signal for permitting operation with MC_A11 closed.

[0093] Reference numeral 82 denotes a logical AND circuit that takes the logical AND of a preset open / close setting signal for MC_A21 and a setting signal for permitting operation with MC_A21 closed.

[0094] Reference numeral 83 denotes a logical AND circuit that takes the logical AND of a preset open / close setting signal of MC_A31 and an operation permission setting signal with MC_A31 closed.

[0095] Reference numerals 84 to 86 denote selectors which select 0 when the output of each of the AND circuits 81 to 83 is 0, and select 1 when the output is 1, and reference numeral 87 denotes an operation permission setting side adder which adds the number which is 1 as the selection result of the selectors 84 to 86.

[0096] Numerals 88 to 90 are selectors which select 0 when the open / close setting signal of MC_A11, the open / close setting signal of MC_A21, and the open / close setting signal of MC_A31 are 0, and select 1 when the open / close setting signal is 1, and 91 is an open / close setting side adder which adds the number when the selection result of selectors 88 to 90 is 1.

[0097] Reference numeral 92 denotes a comparator which outputs 1 only when the sum output of the operation permission setting side adder 87 is equal to 1; 93 denotes a comparator which outputs 1 only when the sum output of the open / close setting side adder 91 is equal to 1.

[0098] Reference numeral 94 denotes a subtractor that takes the difference between the voltage detection value of the output filter capacitor C11 and the secondary side voltage detection value of the output side electromagnetic contactor MC_C11, and reference numeral 95 denotes an absolute value processor that takes the absolute value of the difference output of the subtractor 94.

[0099] Reference numeral 96 denotes a comparator which outputs 1 when the absolute value of the absolute value processor 95 is smaller than a set voltage judgment level.

[0100] Reference numeral 97 denotes a logical AND circuit for generating a load connection permission signal that takes the logical AND of the outputs of the comparators 92, 93, and 96, and outputs a load connection permission signal that specifies permission 1 when the logical AND condition is satisfied and specifies non-permission 0 when the logical AND condition is not satisfied. Reference numeral 98 denotes a selector which selects 0 when the operation permission setting signal in the first electromagnetic contactor MC_A11 during filter capacitor voltage control is not permitted, and selects 1 when it is permitted. Reference numeral 99 denotes a selector which selects 0 when the operation permission setting signal in the second electromagnetic contactor MC_A21 during filter capacitor voltage control is not permitted, and selects 1 when it is permitted. Reference numeral 100 denotes a selector which selects 0 when the operation permission setting signal in the third electromagnetic contactor MC_A31 during filter capacitor voltage control is not permitted, and selects 1 when it is permitted. Reference numeral 101 denotes a second adder on the operation permission setting side that adds up the number for which the selection results of each of the selectors 98 to 100 are 1, and reference numeral 102 denotes a comparator that outputs 1 only when the addition output of the adder 101 is equal to 1. Reference numeral 103 denotes a logical AND circuit which takes the logical AND of the load connection permission signal output from the logical AND circuit 97 and the opening / closing setting signal of MC_A11, reference numeral 104 denotes a logical AND circuit which takes the logical AND of the load connection permission signal output from the logical AND circuit 97 and the opening / closing setting signal of MC_A21, and reference numeral 105 denotes a logical AND circuit which takes the logical AND of the load connection permission signal output from the logical AND circuit 97 and the opening / closing setting signal of MC_A31.

[0101] Reference numerals 106 to 108 denote NOT circuits which logically invert the load connection permission signals. Reference numeral 110 denotes a logical AND circuit which takes the logical AND of the output of the NOT circuit 106, the output of the comparator 102, and the operation permission setting signal in MC_A11 during the filter capacitor voltage control.

[0102] Reference numeral 111 denotes a logical AND circuit which takes the logical AND of the output of the NOT circuit 107, the output of the comparator 102, and the operation permission setting signal in MC_A 21 during the filter capacitor voltage control.

[0103] Reference numeral 112 denotes a logical AND circuit which takes the logical AND of the output of the NOT circuit 108, the output of the comparator 102, and the operation permission setting signal in MC_A31 during the filter capacitor voltage control.

[0104] Reference numeral 113 denotes a logical sum circuit that performs logical sum processing on the outputs of the logical sum circuit 103 and the logical sum circuit 110 and outputs an opening / closing command for the first electromagnetic contactor MC_A11.

[0105] Reference numeral 114 denotes a logical sum circuit which performs logical sum processing on the outputs of the logical sum circuit 104 and the logical sum circuit 111 and outputs an opening / closing command for the second electromagnetic contactor MC_A21.

[0106] Reference numeral 115 denotes a logical sum circuit that performs logical sum processing on the outputs of the logical sum circuit 105 and the logical sum circuit 112 and outputs an opening / closing command for the third electromagnetic contactor MC_A31.

[0107] Reference numeral 116 denotes a first selection circuit which performs a logical sum operation on the outputs of the logical product circuits 103 to 105, and outputs 0 when the result is 0, and outputs 1 when the result is 1.

[0108] Reference numeral 117 denotes a second selection circuit which performs a logical sum operation on the outputs of the logical product circuits 110 to 112, and outputs 0 when the result is 0, and 2 when the result is 1.

[0109] An adder 118 is a current control permission signal generating adder that adds the outputs of the first selection circuit 116 and the second selection circuit 117 and outputs a current control permission signal of either current control disallowance, current control, or output filter capacitor voltage control depending on the addition result. The circuits from the selectors 98 to 100 to the adder 118 constitute an opening and closing command / current control permission signal generating unit 119. In FIG. 13, a configuration diagram of the power conversion device 1 is shown, but the power conversion devices 2 and 3 may also have a similar configuration.

[0110] 13, the following configuration is different from that of the second embodiment. The other parts are the same. (1) The difference between the output filter capacitor voltage detection value and the MC_C11 secondary side voltage detection value is processed as an absolute value. If the processed result is smaller than the voltage judgment level, it is set to 1. If it is larger, it is set to 0 (94 to 96). (2) The result of (1) above is added as one of the AND conditions for the load connection permission signal generation process of the second embodiment (97). (3) A setting to enable MC operation during voltage control has been added to make the filter capacitor equal to the load voltage. (4) A configuration in which, for the MC operation permission setting during filter capacitor voltage control, if it is 0, it is set to 0, and if it is 1, it is set to 1, and the output of the operation permission setting of each MC is added and if it is 1, it is set to 1, and if it is not 1, it is set to 0 (98-102). (5) A logical AND is performed on the logically inverted signals of the signals (3) and (4) and the load connection permission signal (110 to 112). (6) A configuration (117) in which the logical sum of the results of (5) for each MC is taken and if it is 0, the result is 0, and if it is 1, the result is 2. (7) As in the second embodiment, a configuration (116) is configured to take a logical sum of the opening and closing commands of each MC and set the result to 0 if the command is 0 and to 1 if the command is 1. (8) An addition process (118) is performed on the results of (6) and (7) above, and the result is used as a current control permission signal.

[0111] The output MC switching control configuration is shown in Fig. 14. In Fig. 14, the output side electromagnetic contactor switching command generation unit 120 is configured as follows. A logical AND circuit 121 takes the logical AND of the switching command of MC_A11 outputted from the logical OR circuit 113 in Fig. 13 and the status signal of MC_A11. A logical AND circuit 122 takes the logical AND of the switching command of MC_A21 and the status signal of MC_A21. A logical AND circuit 123 takes the logical AND of the switching command of MC_A31 and the status signal of MC_A31.

[0112] The logical sum of the logical product results of the logical product circuits 121 to 123 is taken by a logical sum circuit 124. When the load connection permission signal described in Fig. 13 is "disallowed" 0, an MC_C11 open command 0 is selected by a selector 125, and when the load connection permission signal is "allowed" 1, an MC_C11 close command 1 is selected by a selector 125.

[0113] A logical AND circuit 126 takes the logical AND of the outputs of the logical OR circuit 124 and the selector 125, and outputs an opening / closing command for MC_C11.

[0114] In FIG. (1) The logical AND of the switching command of the MC that selects the current rating and the status signal is taken (121 to 123). (2) In each MC, the logical OR is taken for the result of (1) (124). (3) When the load connection permission signal is 0, an MC_C11 open command is issued, and when the load connection permission signal is 1, an MC_C11 close command is issued (125). (4) The logical product of (2) and (3) is taken (126) and used as an MC_C11 opening / closing command.

[0115] 15 shows a basic control configuration diagram of a power conversion device in the third embodiment. A current range switching processing unit 130 in the third embodiment is configured as follows: 131 is a selector which selects 0 when the opening / closing command for the first electromagnetic contactor MC_A11 is 0 and selects 1 when the opening / closing command is 1 (close command), 132 is a selector which selects 0 when the opening / closing command for the second electromagnetic contactor MC_A21 is 0 and selects 2 when the opening / closing command is 1 (close command), and 133 is a selector which selects 0 when the opening / closing command for the third electromagnetic contactor MC_31 is 0 and selects 3 when the opening / closing command is 1 (close command).

[0116] An adder 134 adds (adds a number that is a close command) the outputs of the selectors 131 to 133. A current detection value setter 135 sets, according to the output of the adder 134, the current detection value of the first current detector HCT_A11, the current detection value of the second current detector HCT_A21, or the current detection value of the third current detector HCT_A31.

[0117] Reference numeral 136 denotes a selector which selects 0 when the current control permission signal output from the adder 118 in FIG. 13 is 0: when current control is not permitted, selects current command 1 when current control is performed, or selects output current command 2 when filter capacitor voltage control is performed.

[0118] In the current controller 140 of the third embodiment, when the current control permission signal is current control 1, the current controller 140 performs proportional control and integral control using the set proportional gain Kp and integral gain Ki so that the current detection value selected by the current range switching processing unit 130 becomes the set current command value, thereby generating a voltage command for the power conversion device, and when the current control permission signal is output filter capacitor voltage control 2, the current controller 140 performs proportional control and integral control using the set proportional gain and integral gain so that the current detection value selected by the current range switching processing unit 130 becomes the set current command value for output filter capacitor voltage control, thereby generating a voltage command for the power conversion device, and when the current control permission signal is current control non-permission 0, the current command, the proportional gain, and the integral gain are switched to zero. 42 is a delay unit, and 43 is a limiter.

[0119] In the case of the main circuit configuration of this embodiment, if the voltages of the output filter capacitors (C11 to C13) and the load 200 are not equal when connecting the main circuit to the load 200, the following state occurs. For this reason, it is necessary to perform output filter capacitor voltage control so that the voltages of the output filter capacitors and the load are equal before connecting the main circuit to the load. (1) If the voltage of the output filter capacitor is higher than the voltage of the load, current will flow to the load side, which may damage the load. (2) If the voltage of the output filter capacitor is lower than the voltage of the load, current will flow to the main circuit side, causing an abnormal current to flow in the components connected between the output filter capacitor and the load, which may damage the components.

[0120] Next, the HCT selection MC switching control will be described. The operation during current control is unchanged from the second embodiment. In this embodiment, three units are described in parallel. The truth table of the load connection permission signal in this embodiment is shown in Table 8.

[0121] [Table 8]

[0122] In this embodiment, the condition for the load connection permission signal to be 0 or 1 is that the difference between the output filter capacitor voltage detection value and the MC_C11 secondary side voltage detection value is equal to or less than the voltage determination level (94, 95, 96 in FIG. 13). This added process is to confirm that the voltage of the output filter capacitor has become equal to the voltage of the load.

[0123] By checking Truth Table 8, it can be seen that when the difference between the output filter capacitor voltage detection value and the MC_C11 secondary side voltage detection value is equal to or lower than the voltage determination level and the load connection permission signal in the second embodiment is 1, the load connection permission signal in the third embodiment is 1. Thus, by using the load connection permission signal in this embodiment, the above states (1) and (2) can be avoided.

[0124] Table 9 shows the truth table of the MC opening and closing command when the load connection permission signal is 0, and Table 10 shows the truth table of the current control permission signal.

[0125] [Table 9]

[0126] [Table 10]

[0127] As shown in Table 9, when the load connection permission signal is 0, the MC opening and closing command of the MC that is permitted to operate with filter capacitor voltage control will be 1. Also, in Table 10, the current control permission signal will be 1 if any of the MC opening and closing commands are 1 when the load connection permission signal is 1. 1 means that current control is permitted. When the load connection permission signal is 0, the signal will be 2 if any of the MC opening and closing commands are 1. 2 means that current control for output filter capacitor voltage control is permitted. In all other cases, the signal will be 0. 0 means that current control is not permitted.

[0128] It can be confirmed that when the load connection permission signal is 0, the current control permission signal is 0 or 2. When the load connection permission signal is 1, it can be confirmed that the current control permission signal is 0 or 1.

[0129] Table 11 shows the truth table for output MC switching control.

[0130] [Table 11]

[0131] These are the MC opening and closing commands, but because exclusive processing is performed in the HCT selection MC opening and closing control, two or more of these signals will never be 1 at the same time. It can be seen that MC_C11 will only be 1 when the load connection permission signal is 1, the opening and closing commands of each MC are 1, and the status signal is also 1. This means that the output MC will operate after the HCT selection is properly made, and will be connected to the load.

[0132] Next, the action and operation of the control configuration will be described. There is no change from the second embodiment in the current range switching process. There is no change from the second embodiment in the operation when the current control permission signal is 0 or 1. The operation differs when the current control permission signal is 2.

[0133] A case where the current control permission signal is 2 will be described. In this case, filter capacitor voltage control is performed. A current command output from the filter capacitor voltage control is set to the input section of the current detector 140 in Fig. 15. Kp is set as the proportional gain, and the integral term is configured to perform feedback of the previous value.

[0134] For example, power conversion device 1 is set to be permitted to operate with MC_A11, MC_A21, and MC_A31, power conversion device 2 is permitted to operate with MC_A12 and MC_A22, and power conversion device 3 is permitted to operate with MC_A13. In this case, since each control operates as described above, when the current rating is large, operation is performed with power conversion devices 1, 2, and 3. Next, when the current rating is small, operation is performed with power conversion devices 1 and 2, and power conversion device 3 performs output filter capacitor voltage control. When the current rating is the smallest, operation is performed with only power conversion device 1, and power conversion devices 2 and 3 perform output filter capacitor voltage control. This makes it possible to operate by switching the current rating even when the circuit configuration has a capacitor in the output section.

[0135] As described above, according to the third embodiment, in a configuration in which multiple units having a capacitor at the output of a power conversion device are connected in parallel, in an area where multiple units with a large current rating are required to be operated, multiple units can be operated in parallel. In an operating area where the operable current is small according to each current rating, an appropriate number of units can be operated. This reduces the carrier ripple, thereby reducing harmonics caused by the carrier. EXAMPLES

[0136] Fig. 16 shows a main circuit configuration diagram of a power converter in Example 4. In Fig. 16, three power converters 1, 2, and 3 are provided in parallel to a load 200. In an electric path connecting the power converter 1 and the load 200, a first current detector HCT_A11 on the front side of an output filter having a first current rating, a first reactor L_A11, a first electromagnetic contactor MC_A11 on the front side of an output filter that selects the first current detector, a first electromagnetic contactor MC_B11 on the rear side of an output filter that selects the first current detector on the rear side of the output filter, a first current detector HCT_B11 on the rear side of an output filter having a first current rating, a fourth reactor L_B11, and an output side electromagnetic contactor MC_C11 are connected in series in this order from the power converter 1 to the load 200.

[0137] The series circuit of L_A11 and MC_A11 is connected in parallel with a series circuit consisting of a second current detector HCT_A21 on the front side of the output filter having a second current rating smaller than the first current detector, a second reactor L_A21, and a second electromagnetic contactor MC_A21 on the front side of the output filter that selects the second current detector, and a series circuit consisting of a third current detector HCT_A31 on the front side of the output filter having a third current rating smaller than the second current detector, a third reactor L_A31, and a third electromagnetic contactor MC_A31 on the front side of the output filter that selects the third current detector.

[0138] An output filter capacitor C11 is connected between the common connection point of MC_A11 and MC_B11 and the negative terminal of the power conversion device.

[0139] A series circuit consisting of a second current detector HCT_B21 and MC_B21 on the rear side of the output filter having a second current rating, and a series circuit consisting of a third current detector HCT_B31 and MC_B31 on the rear side of the output filter having a third current rating are connected in parallel between both ends of MC_B11.

[0140] The circuits between the power conversion devices 2, 3 and the load 200 are configured in the same manner as above, with the last numbers of each part being changed from 1 to 2, 3.

[0141] In Fig. 16, the current rating is three, and the number of parallel power conversion devices is three. However, as in the second embodiment, the number of HCTs and MCs per device and the number of parallel power conversion devices can be up to N. The main circuit configuration diagram has the following features. (1) The output filter has HCTs before and after it. The one before the filter is HCT_A, and the one after the filter is HCT_B. (2) The combination of current rating, HCT, and MC is defined as shown in Table 12.

[0142] [Table 12]

[0143] Table 12 shows only one unit, but other power conversion devices are defined in the same way.

[0144] The main circuit configuration of this embodiment is one that has a capacitor at the output. In this example, the output filter is LCL. Also, a switch is provided after the L in the final stage of the LCL to separate it from the load.

[0145] Fig. 17 shows a configuration diagram of the HCT selection MC switching control in the fourth embodiment. In Fig. 17, the same parts as in Fig. 13 are indicated by the same reference numerals. In Fig. 17, the following configuration differs from the third embodiment. The other parts are the same. Here, the configuration diagram of the power conversion device 1 is shown, but the power conversion devices 2 and 3 may also have the same configuration. (1) Regarding MC_A11, the open / close setting, the operation permission setting when closed, the operation permission setting with filter capacitor voltage control, and the open / close command have been changed to MC_A11 and MC_B11. (2) Regarding MC_A21, the open / close setting, the operation permission setting when closed, the operation permission setting with filter capacitor voltage control, and the open / close command have been changed to MC_A21 and MC_B21. (3) Regarding MC_A31, the open / close setting, the operation permission setting when closed, the operation permission setting with filter capacitor voltage control, and the open / close command have been changed to MC_A31 and MC_B31.

[0146] The output MC switching control configuration is shown in Fig. 18. In Fig. 18, the same parts as in Fig. 14 are designated by the same reference numerals. In Fig. 18, the changes from the third embodiment are as follows. (1) The opening and closing commands and status signals for MC_A11 have been changed to MC_A11 and MC_B11. (2) The opening and closing commands and status signals for MC_A21 have been changed to MC_A21 and MC_B21. (3) The opening and closing commands and status signals for MC_A31 have been changed to MC_A31 and MC_B31.

[0147] Fig. 19 shows a basic control configuration diagram of a power conversion device in the fourth embodiment. In Fig. 19, the same parts as in Fig. 15 are designated by the same reference numerals. A current range switching processing unit 150 in the fourth embodiment is configured as follows.

[0148] Reference numeral 151 denotes a selector which outputs 0 or 1 in response to an opening / closing command for the first electromagnetic contactor MC_A11 on the front side of the output filter and the first electromagnetic contactor MC_B11 on the rear side of the output filter; 152 denotes a selector which outputs 0 or 2 in response to an opening / closing command for the second electromagnetic contactor MC_A21 on the front side of the output filter and the second electromagnetic contactor MC_B21 on the rear side of the output filter; and 153 denotes a selector which outputs 0 or 3 in response to an opening / closing command for the third electromagnetic contactor MC_A31 on the front side of the output filter and the third electromagnetic contactor MC_B31 on the rear side of the output filter.

[0149] An adder 154 adds the outputs of the selectors 151 to 153. An output filter front-side selector 155 selects each current detection value of the output filter front-side current detectors HCT_A11, HCT_A21, and HCT_A31 in response to the output of the adder 154.

[0150] Reference numeral 156 denotes an output filter rear side selector which selects each current detection value of the output filter rear side current detectors HCT_B11, HCT_B21, and HCT_B31 in response to the output of the adder 154.

[0151] The selected output (current detection value) of the output filter front side selector 155 is used as a feedback signal on the proportional control side of a current controller 158 .

[0152] The output (current detection value) side of the output filter rear side selector 156 is connected to a 1 side terminal of a selector 157 which switches the current detection value according to the current control permission signal of 0, 1, or 2. The 0 side terminal and the 2 side terminal of the selector 157 are connected to the output terminal of the output filter front side selector 155.

[0153] The selected output (current detection value) of the selector 157 is used as a feedback signal for the integral control side of the current controller 158 .

[0154] The current controller 158 in the fourth embodiment performs the following operations: When the current control permission signal is current control, proportional control is performed by a set proportional gain for current control so that the current detection value of the output filter front-side current detector selected by the output filter front-side selector 155 becomes the set current command value, and integral control is performed by a set integral gain for current control so that the current detection value of the output filter rear-side current detector selected by the output filter rear-side selector 156 becomes the set current command value, thereby generating a voltage command for the power conversion device; when the current control permission signal is output filter capacitor voltage control, proportional control and integral control are performed by a set proportional gain and integral gain for output filter capacitor voltage control so that the current detection value of the output filter front-side current detector selected by the output filter front-side selector 155 becomes the set current command value for output filter capacitor voltage control, thereby generating a voltage command for the power conversion device; when the current control permission signal is current control prohibition, the current command, the proportional gain, and the integral gain are switched to zero.

[0155] In FIG. 19, the differences from the third embodiment are as follows. (1) When the current control permission signal is 0, the current command and the proportional gain and integral gain of the current control are set to 0. (2) The feedback signals used for the proportional control and integral control of the current control are different. (3) The feedback signal used for the proportional control of the current control is HCT_A11, HCT_A21, or HCT_A31. (4) The feedback signal used for integral control of current control is switched according to the current control permission signal. When the current control permission signal is 0 or 2, it is HCT_A11, HCT_A21, or HCT_A31. When the current control permission signal is 1, it is HCT_B11, HCT_B21, or HCT_B31.

[0156] Although this is an HCT selection MC opening and closing control, the basic operation is the same as in the third embodiment. The following are changes from the third embodiment. ·MC_A11, MC_A21, and MC_A31 simultaneously control the opening and closing of MCs with the rating combinations shown in Table 12 above.

[0157] Combinations that produce the same switching operation are "MC_A11 and MC_B11", "MC_A21 and MC_B21", and "MC_A31 and MC_B31". This allows the appropriate MC to be switched according to the selected current rating.

[0158] Although this is an output MC switching control, the basic operation is the same as in Example 3. In this configuration, the switching commands and status signals of MC_B11, MC_B21, and MC_B31, which are MCs added to the main circuit, are also taken into consideration. For this reason, in this main circuit as well, the output MC operates after the HCT selection is appropriately performed, making it possible to connect to the load.

[0159] The operation of current control is explained below. We will explain current control. Proportional control is the dominant control in order to speed up response, so the current detection value detected by the HCT before the filter, from which high-frequency components have not been removed, is set as the feedback signal. Integral control is the dominant control in order to eliminate steady-state deviation, so the current detection value detected by the HCT after the filter, from which high-frequency components have been removed and from which low-frequency regions can be detected with high accuracy, is set as the feedback signal. This makes it possible to achieve high-response, highly accurate current control. On the other hand, when controlling the voltage of the output filter capacitor, the current detection value detected by the HCT before the filter is set as the feedback signal for proportional control and integral control in order to control the current value flowing into the filter capacitor.

[0160] As described above, according to the fourth embodiment, even when the main circuit configuration of this embodiment is used to improve the current control accuracy, in the region where multiple units with a large current rating are required, multiple units can be operated in parallel. In the operating region where the operable current is small according to each current rating, an appropriate number of units can be operated. This reduces the carrier ripple, and therefore the harmonics caused by the carrier can be reduced. EXAMPLES

[0161] In the fifth embodiment, the configuration of the main circuit between a plurality of power conversion devices and a load, the configuration of the HCT selection MC switching control, and the configuration of the output MC switching control are unchanged from the fourth embodiment, but the basic control configuration is changed. Fig. 20 shows the basic control configuration of the power conversion device in the fifth embodiment.

[0162] In Fig. 20, the same parts as in Fig. 19 are denoted by the same reference numerals. Reference numeral 160 denotes a current command enable / disable selection circuit which enables the current command on the input side of the current controller 158 (terminal 1 of selector 136) only when all of the output side electromagnetic contactors connected in parallel are in the closed state when a current control permission signal specifying current control is output, and is configured as follows.

[0163] Reference numeral 161 denotes a logical AND circuit which takes the logical AND of the state signals (0: open, 1: closed) of the output side electromagnetic contactors MC_C11, MC_C12, and MC_C13. Reference numeral 162 denotes a selector which selects 0 when the output of the logical AND circuit 161 is 0, and selects a current command when the output is 1, and the output side of the selector 162 is connected to the 1 side terminal of the selector 136. The other parts are configured in the same way as in FIG.

[0164] The switching operation of the output MC varies from part to part. In a large-capacity MC, it may take tens to hundreds of ms from when a switching signal is input until it actually operates. For this reason, unless a current command is received after all output MCs are turned ON, the timing at which the output current of each device connected in parallel rises will differ. There is a problem in that it takes a long time for the total output current value to reach the command value. Figure 21 shows a current waveform when not all output MCs are ON. Here, a case is shown in which the output MC of power conversion device 1 is turned ON, then the output MC of power conversion device 3 is turned ON, and finally the output MC of power conversion device 2 is turned ON.

[0165] The current waveform when the configuration of this embodiment is applied is shown in Fig. 22. Since the current command changes after all output MCs are closed, it can be seen that the time from when the command value changes until the total value of the output current reaches the target value is shortened.

[0166] As described above, according to the fifth embodiment, in the case where the response speed is defined by the time from when the command value changes until the output current reaches the target current, the response speed of the output current can be increased. EXAMPLES

[0167] In the sixth embodiment, the main circuit configuration between multiple power conversion devices and loads, the HCT selection MC switching control, the output MC switching control, and the control configuration are not changed from the fifth embodiment. A process for determining the operation permission setting at each MC closed for the HCT selection MC switching control has been newly added. Here, MC_A11 and MC_B11, MC_A12 and MC_B12, and MC_A13 and MC_B13 are described, but by adopting a similar configuration for the other MCs, the number of switching times for the MCs between parallel devices can be made uniform. Figure 23 shows the configuration diagram for processing the number of switching times for each MC.

[0168] In FIG. 23, 165a is a selector that selects 0 or 1 in response to the status signals of MC_A11 and MC_B11 (0: open, 1: closed), 165b is a selector that selects 0 or 1 in response to the status signals of MC_A12 and MC_B12 (0: open, 1: closed), and 165c is a selector that selects 0 or 1 in response to the status signals of MC_A13 and MC_B13 (0: open, 1: closed).

[0169] Reference numeral 166a denotes a counter that counts the number of times that the selector 165a outputs one signal and outputs the number of times that MC_A11 and MC_B11 open and close, reference numeral 166b denotes a counter that counts the number of times that the selector 165b outputs one signal and outputs the number of times that MC_A12 and MC_B12 open and close, and reference numeral 166c denotes a counter that counts the number of times that the selector 165c outputs one signal and outputs the number of times that MC_A13 and MC_B13 open and close.

[0170] In Fig. 23, counting is performed according to the status signal of the MC. If the status signal is 0, counting is not performed, and if the status signal is 1, the number of times is incremented by 1. Figure 24 shows the configuration diagram of operation permission setting when each MC is closed. The configuration is such that the operation permission setting according to the number of parallel units set when the MC is closed is selected by selector 167 and the operation permission setting for each MC is output. Since the maximum number of units in parallel operation is three, selection is made according to whether one unit, two units, or three units are used.

[0171] Figure 25 shows the operation permission settings for one parallel unit. For the MCs in parallel, the number of openings and closings is compared, and the MC with the smallest number is set to have the operation permission setting in closed mode set to 1. For MCs other than those with the smallest number of openings and closings, the operation permission setting in closed mode is set to 0. Also, when the number of openings and closings is the same, priority is given to those with the operation permission setting in closed mode of 1, so that no more MCs than the number of units are turned ON.

[0172] In FIG. 25, 168 is a comparator that compares the number of openings and closings between MC_A11 and MC_B11 counted by counter 166a in FIG. 23 with the number of openings and closings between MC_A12 and MC_B12 counted by counter 166b in FIG. 23, and 169 is a selector that selects the number of openings and closings between MC_A11 and MC_B11 (0) or the number of openings and closings between MC_A12 and MC_B12 (1) depending on the comparison result of comparator 168.

[0173] Reference numeral 170 denotes a comparator which compares the number of openings and closings of MC_A13 and MC_B13 counted by counter 166c in FIG. 23 with the output of selector 169, and reference numeral 171 denotes a selector which selects either the output (0) of selector 169 or the number of openings and closings of MC_A13 and MC_B13 (1) depending on the comparison result of comparator 170.

[0174] 172a is a determinator that determines whether the number of opening and closing times of MC_A11 and MC_B11 is equal to the output of the selector 171, 172b is a determinator that determines whether the number of opening and closing times of MC_A12 and MC_B12 is equal to the output of the selector 171, and 173c is a determinator that determines whether the number of opening and closing times of MC_A13 and MC_B13 is equal to the output of the selector 171.

[0175] 173a is a selector that selects 0 or 1 according to the decision output of the decider 172a, 173b is a selector that selects 0 or 1 according to the decision output of the decider 172b, and 173c is a selector that selects 0 or 1 according to the decision output of the decider 172c.

[0176] A selector 174 selects either the selected output of the selector 173b or 0 according to the selected output of the selector 173a.

[0177] Reference numeral 175 denotes a logical sum circuit that performs logical sum processing on the outputs of the selector 173 a and the selector 174 .

[0178] A selector 176 selects the selected output of the selector 173 c or 0 according to the output of the OR circuit 175 .

[0179] The selection output of the selector 173a becomes an operation permission setting signal when MC_A11 and MC_B11 are closed, the selection output of the selector 174 becomes an operation permission setting signal when MC_A12 and MC_B12 are closed, and the selection output of the selector 176 becomes an operation permission setting signal when MC_A13 and MC_B13 are closed.

[0180] Figure 26 shows the operation permission settings for two parallel units. For the MCs in parallel, the number of openings and closings is compared, and the operation permission setting in closed state is set to 1 for the MC with the smallest number of openings and closings and the MC with the second smallest number of openings and closings. The operation permission setting in closed state for the MC with the most number of openings and closings is set to 0. Also, when the number of openings and closings is the same, priority is given to those with an operation permission setting of 1 in closed state, so that no more MCs than the number of units are turned on.

[0181] In FIG. 26, 177 is a comparator that compares the number of openings and closings between MC_A11 and MC_B11 with the number of openings and closings between MC_A12 and MC_B12, and 178 is a selector that selects the number of openings and closings between MC_A11 and MC_B11 (1) or the number of openings and closings between MC_A12 and MC_B12 (0) depending on the comparison result of comparator 177.

[0182] Reference numeral 179 denotes a comparator which compares the selection output of the selector 178 with the number of openings and closings of MC_A13 and MC_B13, and reference numeral 180 denotes a selector which selects either the selection output (0) of the selector 178 or the number of openings and closings of MC_A13 and MC_B13 (1) depending on the comparison result of the comparator 179.

[0183] Reference numeral 181 denotes a selector which selects, depending on the comparison result of the comparator 177, the number of openings and closings between MC_A11 and MC_B11 (0) or the number of openings and closings between MC_A12 and MC_B12 (1).

[0184] Reference numeral 182 denotes a determiner that judges whether the number of times MC_A11 and MC_B11 are opened and closed is equal to the selection output of the selector 181, and reference numeral 183 denotes a determiner that judges whether the number of times MC_A11 and MC_B11 are opened and closed is equal to the selection output of the selector 181.

[0185] 184a is a determinator that determines whether the number of opening and closing times of MC_A11 and MC_B11 is equal to the selection output of the selector 180, 184b is a determinator that determines whether the number of opening and closing times of MC_A11 and MC_B11 is equal to the selection output of the selector 180, and 184c is a determinator that determines whether the number of opening and closing times of MC_A12 and MC_B12 is equal to the selection output of the selector 180.

[0186] Reference numeral 185 denotes a logical OR circuit which performs logical OR processing of the respective decision outputs of the determinator 184 a and the determinator 182 , and reference numeral 186 denotes a logical OR circuit which performs logical OR processing of the respective decision outputs of the determinator 184 b and the determinator 183 .

[0187] Reference numeral 187a denotes a selector which selects 0 or 1 according to the output of the logical sum circuit 185, 187b denotes a selector which selects 0 or 1 according to the output of the logical sum circuit 186, and 187c denotes a selector which selects 0 or 1 according to the decision output of the decision circuit 184c.

[0188] Reference numeral 188 denotes a logical sum circuit which takes the logical product of the selection output of the selector 187a and the selection output of the selector 187b, and reference numeral 189 denotes a selector which selects either the selection output of the selector 187c or 0 according to the output of the logical sum circuit 188.

[0189] The selection output of the selector 187a becomes an operation permission setting signal with MC_A11 and MC_B11 closed, the selection output of the selector 187b becomes an operation permission setting signal with MC_A12 and MC_B12 closed, and the selection output of the selector 189 becomes an operation permission setting signal with MC_A13 and MC_B13 closed.

[0190] Figure 27 shows the operation permission setting for the number of parallel units being 3. In this case, since this is the same as the number of parallel units, the number of openings and closings is equal between the devices. For this reason, the operation permission is set to 1. In each MC opening and closing count process in Figure 23, processing is performed to count the number of openings and closings according to the MC status signal. Since the count is based on the status signal, the actual number of MC opening and closings can be counted correctly.

[0191] The operation permission setting with each MC closed will be explained. The process of equalizing the number of switching times differs depending on the number of parallel units. In the case of 3 parallel units, if the number of parallel units is 1, the number of switching times can be equalized by always selecting the MC with the smallest number of switching times. If the number of parallel units is 2, the number of switching times can be equalized by selecting the MC with the smallest or second largest number of switching times. If the number of parallel units is 3, there is no bias in the number of switching times between the devices, so no special process is required to equalize the number of switching times. In this way, the MC operation permission setting differs to equalize the number of parallel units. With the configuration shown in Figure 24, the process of operation permission setting can be changed depending on the number of parallel units during MC operation, which is set in advance, so that the optimal process can be selected.

[0192] The operation permission settings when the number of parallel units is 1 will be described. In Fig. 25, first the number of opening and closing times between MC_A11 and MC_B11 is compared with that between MC_A12 and MC_B12. The number of opening and closing times of the MC with the smallest number of opening and closing times is then compared with that between MC_A13 and MC_B13. The MC with the smallest number of opening and closing times as a result of this comparison will have the smallest number of opening and closing times. The operation permission setting in closed state for the MC with the smallest number of opening and closing times is set to 1. The operation permission setting in closed state for the other MCs is set to 0. If the number of opening and closing times is equal, the operation permission settings are prioritized. In this example, the order of priority is highest for MC_A11 and MC_B11, followed by MC_A12 and MC_B12, and finally MC_A13 and MC_B13.

[0193] Table 13 shows an example of the number of switching operations before and after a change when the number of parallel units is 1.

[0194] [Table 13]

[0195] The operation permission setting for the case where the number of parallel units is 2 will be described. In FIG. 26, first, the number of openings and closings of MC_A11 and MC_B11 are compared with the number of openings and closings of MC_A12 and MC_B12. The MC with the smallest number of openings and closings as a result of the comparison is the MC with the smallest or second largest number of openings and closings, so the operation permission setting in closed state is set to 1. The number of openings and closings of MC_A13 and MC_B13 are compared with the MC with the smallest number of openings and closings as a result of the comparison. The MC with the smallest number of openings and closings as a result of the comparison is the MC with the smallest or second largest number of openings and closings, so the operation permission setting in closed state is set to 1. The operation permission setting in closed state for the other MCs is set to 0. When the number of openings and closings is equal, the operation permission settings are prioritized. In this example, only MC_A13 and MC_B13 are given low priority.

[0196] Table 14 shows an example of the number of switching operations before and after the change when there are two parallel units.

[0197] [Table 14]

[0198] The operation permission setting will be described when the number of parallel units is 3. In this case, since there is no difference in the number of MC opening and closing times between the devices, the operation permission setting for MC_A11 and MC_B11, MC_A12 and MC_B12, and MC_A13 and MC_B13 closed is set to 1.

[0199] As described above, according to the sixth embodiment, the number of times each MC is opened and closed is determined, and the number of times each MC is opened and closed can be made uniform, so that the life of the device can be expected to be extended. EXAMPLES

[0200] A main circuit configuration diagram of this embodiment is shown in Fig. 28. Here, three devices are connected in parallel, and a current range switching circuit is not provided at the outputs of power conversion device 2 and power conversion device 3.

[0201] In Fig. 28, the same parts as in Fig. 16 are denoted by the same reference numerals. The difference between Fig. 28 and Fig. 16 is that HCT_A21, HCT_A31, L_A21, L_A31, MC_A21, MC_A31, MC_B21, MC_B31, HCT_B21, and HCT_B31 between the power conversion devices 2 and 3 and the load 200 are deleted, the current range switching processing unit is deleted in the power conversion devices 2 and 3, and the feedback input to the current controller is only the current detection value of the first current detector, and the other parts are configured the same as in Fig. 16. There are no changes from the fifth embodiment in other parts regarding the HCT selection MC opening and closing control, the output MC opening and closing control, and the control configuration.

[0202] In Fig. 28, when the current rating is medium and small, and is smaller than the rated current of one power conversion device, parallel operation is not necessary. In this case, driving one device improves control accuracy because the carrier ripple can be reduced. A circuit that switches the current rating is provided only for the output of a specific power conversion device (in this embodiment, on the power conversion device 1 side). When driving this circuit, operation is possible if the operation permission setting when the MC (MC_A21, MC_A31, MC_B21, MC_B31) is closed when selecting medium and small current ratings in the HCT selection MC opening and closing control is set to not permitted.

[0203] As described above, according to the seventh embodiment, it is possible to reduce the number of parts by deleting unnecessary circuits, thereby reducing costs and panel size. EXAMPLES

[0204] In the embodiment 8, there are no changes in the main circuit configuration, HCT selection MC switching control, output MC switching control, and control configuration from the embodiment 5. FIG. 29 shows the carrier frequency selection process when MC_A11 and MC_B11 are selected.

[0205] In FIG. 29, 191 is a comparator that compares the rated current of the power conversion device with the rated current when the front first electromagnetic contactor MC_A11 and the rear first electromagnetic contactor MC_B11 of the output filter are selected, 192 is a comparator that compares the current obtained by dividing the rated current of the power conversion device by the first set number (2) with the rated current when the first electromagnetic contactors MC_A11 and MC_B11 are selected, and 193 is a comparator that compares the current obtained by dividing the rated current of the power conversion device by the second set number (3) with the rated current when the first electromagnetic contactors MC_A11 and MC_B11 are selected.

[0206] Reference numeral 194a denotes a selector which selects 1 if the comparison result of comparator 191 shows that the rated current when MC_A11 and MC_B11 are selected is smaller, and selects 0 if it is larger; reference numeral 194b denotes a selector which selects 2 if the comparison result of comparator 192 shows that the rated current when MC_A11 and MC_B11 are selected is smaller, and selects 0 if it is larger; and reference numeral 194c denotes a selector which selects 4 if the comparison result of comparator 193 shows that the rated current when MC_A11 and MC_B11 are selected is smaller, and selects 0 if it is larger.

[0207] Reference numeral 195 denotes an adder that adds the selection outputs of the selectors 194a to 194c, and reference numeral 196 denotes a selector that selects carrier frequency 1 when the addition output of adder 195 is 0 or 1, selects carrier frequency 2 higher than carrier frequency 1 when the addition output is 3, and selects carrier frequency 3 higher than carrier frequency 2 when the addition output is 7. The selection output of selector 196 becomes the carrier frequency when MC_A11 and MC_B11 are selected.

[0208] When MC_A21 and MC_B21 are selected, and when MC_A31 and MC_B31 are selected, the carrier frequency selection is configured in the same manner as in FIG.

[0209] In FIG. 29, the rated current of the power converter is compared with the rated current when MC_A11 and MC_B11 are selected, and if the rated current when MC_A11 and MC_B11 are selected is small, 1 is selected, and if it is large, 0 is selected. The rated current when MC_A11 and MC_B11 are selected is compared with 1 / 2 times the rated current of the power converter, and if the rated current when MC_A11 and MC_B11 are selected is small, 2 is selected, and if it is large, 0 is selected. The rated current when MC_A11 and MC_B11 are selected is compared with 1 / 3 times the rated current of the power converter, and if the rated current when MC_A11 and MC_B11 are selected is small, 4 is selected, and if it is large, 0 is selected. The results of each comparison are added, and if the addition result is 0 or 1, carrier frequency 1 is set as the carrier frequency when MC_A11 and MC_B11 are selected, if it is 3, carrier frequency 2 is set as the carrier frequency when MC_A11 and MC_B11 are selected, and if it is 7, carrier frequency 3 is set as the carrier frequency when MC_A11 and MC_B11 are selected. The carrier frequency selection when each MC is selected may be configured in the same way. FIG. 30 shows the carrier frequency setting in the eighth embodiment.

[0210] In FIG. 30, 197 is a selector that selects the carrier frequency when MC_A11 and MC_B11 are selected (the carrier frequency selected by the circuit in FIG. 29) when the MC_A11 and MC_B11 opening and closing command is 1. A selector 198 selects a carrier frequency when MC_A21 and MC_B21 are selected (a carrier frequency selected by a circuit similar to that in FIG. 29) when the MC_A21 and MC_B21 opening and closing command is 1. A selector 199 selects a carrier frequency when MC_A31 and MC_B31 are selected (a carrier frequency selected by a circuit similar to that in FIG. 29) when the MC_A31 and MC_B31 opening and closing command is 1.

[0211] In Figure 30, when the MC_A11 and MC_B11 opening and closing command is 1, the carrier frequency is set to the carrier frequency when MC_A11 and MC_B11 are selected; when the MC_A21 and MC_B21 opening and closing command is 1, the carrier frequency is set to the carrier frequency when MC_A21 and MC_B21 are selected; and when the MC_A31 and MC_B31 opening and closing command is 1, the carrier frequency is set to the carrier frequency when MC_A31 and MC_B31 are selected.

[0212] The carrier frequency at which a power conversion device can operate continuously without problems when outputting the rated current of a single power conversion device is defined as the rated current carrier frequency of the power conversion device. As the carrier frequency increases, the loss of the power conversion device increases and the current that can be passed decreases. In other words, when the current is small, it is possible to increase the carrier frequency.

[0213] In the carrier frequency selection process when MC_A11 and MC_B11 are selected in FIG. 29, the rated current when MC_A11 and MC_B11 are selected is compared with the rated current of the power conversion device, 1 / 2 the rated current, and 1 / 3 the rated current. If the rated current when MC_A11 and MC_B11 are selected is smaller than 1 / 2 the rated current, it is possible to increase the carrier frequency. Although it depends on the design, it is possible to make it approximately twice the rated current carrier frequency of the power conversion device. This value is called carrier frequency 2. If the rated current when MC_A11 and MC_B11 are selected is smaller than 1 / 2 the rated current, it is possible to make it approximately three times the rated current carrier frequency of the power conversion device, although it depends on the design. This value is called carrier frequency 3. The carrier frequency is increased according to the rated current value when MC_A11 and MC_B11 are selected.

[0214] The carrier frequency of the device must be set appropriately according to the rated current when each MC is selected. By performing the process shown in Figure 30, the carrier frequency can be set according to the rated current when each MC is selected, depending on the open / close selection of each MC. The MC for connecting to the load opens and closes upon receiving a command after the open / close state of each MC has been determined. For this reason, if the carrier frequency is set according to the open / close command of each MC, it is possible to change the carrier frequency before the output MC opens and closes. For example, even if current pulsation occurs when changing the carrier frequency, it does not affect the load because the output MC is not open or closed.

[0215] As described above, according to the eighth embodiment, it is possible to change the carrier frequency without generating current pulsation in the load, and it is possible to reduce the carrier ripple without generating harmonics due to a sudden change in current or increasing the carrier frequency. [Explanation of symbols]

[0216] 1, 2, 3...Power converter 200…load HCT_A11, HCT_A21, HCT_A31…Current detectors MC_A11, MC_A21, MC_A31, MC_C11...Magnetic contactor L_A11, L_A12, L_B11, L_B12, L_A21...Reactors 10, 50, 80...Load connection permission determination processing unit 11, 12, 15, 32, 51a to 51n, 58, 59a to 59n, 81 to 83, 97, 118, 126...Logical AND circuit 30, 70, 130, 150...Current range switching processing section 40, 140, 158...Current controller 53, 55, 72, 87, 91, 101, 118, 134, 154…Adder 56, 57, 92, 93, 96, 102...Comparators 60,113~115,124…OR circuit 61,119…Opening and closing command / current control permission signal generator 120…Output side magnetic contactor opening / closing command generation unit 155...Output filter front selector 156...Output filter rear selector

Claims

1. a first current detector having a first current rating, a first reactor, and a first electromagnetic contactor for selecting the first current detector, which are respectively inserted in an electric path connecting each of the power conversion devices and the load and are connected in series from the power conversion device to the load; a second current detector having a second current rating smaller than that of the first current detector, a second reactor, and a second electromagnetic contactor for selecting the second current detector, which are connected in series between both ends of the first electromagnetic contactor; a load connection permission determination processing unit including: a first magnetic contactor side AND circuit which takes a logical AND of a preset opening / closing setting signal of the first magnetic contactor and an operation permission setting signal when the first magnetic contactor is closed; a second magnetic contactor side AND circuit which takes a logical AND of a preset opening / closing setting signal of the second magnetic contactor and an operation permission setting signal when the second magnetic contactor is closed; a first exclusive OR circuit which receives as inputs an output of the first magnetic contactor side AND circuit and an output of the second magnetic contactor side AND circuit; a second exclusive OR circuit which receives as inputs an opening / closing setting signal of the first magnetic contactor and an opening / closing setting signal of the second magnetic contactor; and a load connection permission signal generating AND circuit which takes a logical AND of an output of the first exclusive OR circuit and an output of the second exclusive OR circuit, and outputs a signal which permits load connection when a logical AND condition is established; an opening / closing command / current control permission signal generating unit including: a first electromagnetic contactor opening / closing command generating AND circuit which takes a logical AND of the load connection permission signal output from the load connection permission determination processing unit and the opening / closing setting signal of the first electromagnetic contactor to output an opening / closing command for the first electromagnetic contactor; a second electromagnetic contactor opening / closing command generating AND circuit which takes a logical AND of the load connection permission signal output from the load connection permission determination processing unit and the opening / closing setting signal of the second electromagnetic contactor to output an opening / closing command for the second electromagnetic contactor; and a current control permission signal generating AND circuit which performs a logical OR process on the output of the first electromagnetic contactor opening / closing command generating AND circuit and the output of the second electromagnetic contactor opening / closing command generating AND circuit to generate a current control permission signal; a current range switching processing unit having an exclusive OR circuit to which the first electromagnetic contactor opening / closing command signal and the second electromagnetic contactor opening / closing command signal generated by the opening / closing command / current control permission signal generating unit are input, and a logical AND circuit which takes a logical AND of an output of the exclusive OR circuit and the second electromagnetic contactor opening / closing command signal, and which selects each current detection value of the first current detector or the second current detector in accordance with an output of the logical AND circuit; a current controller that generates a voltage command for the power conversion device by performing proportional control and integral control using set proportional gain and integral gain so that the current detection value selected by the current range switching processing unit becomes a set current command value when the current control permission signal generated by the opening / closing command / current control permission signal generation unit indicates control permission, and switches the current command, proportional gain, and integral gain to zero when the current control permission signal indicates control disallowance.

2. a main circuit of the power conversion device is configured by connecting in parallel a series circuit including the second current detector, the second reactor, and the second electromagnetic contactor between both ends of the first electromagnetic contactor, the number of which corresponds to the number of installed power conversion devices; the second electromagnetic contactor side AND circuit of the load connection permission determination processing unit has AND circuits for taking a logical AND of an open / close setting signal of the second electromagnetic contactor and an operation permission signal when the second electromagnetic contactor is closed, the number of AND circuits being equal to the number of installed power conversion devices; Instead of the first and second exclusive OR circuits and the load connection permission signal generating AND circuit, an operation permission setting side adder that adds up the number of times that each AND result of the first electromagnetic contactor side AND circuit and the second electromagnetic contactor side AND for the number of installed power conversion devices is 1, an opening / closing setting side adder that adds up the number of times that the opening / closing setting signal of the first electromagnetic contactor and the opening / closing setting signal of the second electromagnetic contactor for the number of installed power conversion devices are closed, a first comparator that outputs 1 only when the addition output of the operation permission setting side adder is equal to 1, a second comparator that outputs 1 only when the addition output of the opening / closing setting side adder is equal to 1, and a load connection permission signal generating AND circuit that takes the AND of the outputs of the first comparator and the second comparator and outputs a signal that permits load connection when a AND condition is established, the second electromagnetic contactor opening / closing command generating AND circuit of the opening / closing command / current control permission signal generating unit has AND circuits which take the logical product of a load connection permission signal and an opening / closing setting signal of the second electromagnetic contactor, the number of which corresponds to the number of installed power conversion devices; and the current control permission signal generating OR circuit is composed of OR circuits which perform logical OR processing of an output of the first electromagnetic contactor opening / closing command generating AND circuit and each output of the second electromagnetic contactor opening / closing command generating AND circuit, the number of which corresponds to the number of installed power conversion devices; 2. The power conversion device according to claim 1, wherein the current range switching processing unit has an adder, instead of the exclusive OR circuit, that adds up the number of times that the opening / closing command of the first electromagnetic contactor and the opening / closing command of the second electromagnetic contactor, the number of installed power conversion devices, are close commands, and is configured to select each current detection value of the first current detector or the second electromagnetic contactor, the number of installed power conversion devices, depending on the addition result of the adder.

3. a first current detector having a first current rating, a first reactor, a first electromagnetic contactor for selecting the first current detector, a fourth reactor, and an output side electromagnetic contactor, each of which is inserted in an electric path connecting each of the power converters to the load and connected in series from the power converters to the load; a series circuit consisting of a second current detector having a second current rating smaller than that of the first current detector, a second reactor, and a second electromagnetic contactor for selecting the second current detector, each of which is connected in parallel to the series circuit of the first reactor and the first electromagnetic contactor; a series circuit consisting of a third current detector having a third current rating smaller than that of the second current detector, a third reactor, and a third electromagnetic contactor for selecting the third current detector; and an output filter capacitor connected between a common connection point of the series circuit of the first reactor and the first electromagnetic contactor, the fourth reactor, and a negative terminal of the power converter; a first magnetic contactor side AND circuit which takes a logical AND of a preset opening / closing setting signal of the first magnetic contactor and an operation permission setting signal when the first magnetic contactor is closed; a second magnetic contactor side AND circuit which takes a logical AND of a preset opening / closing setting signal of the second magnetic contactor and an operation permission setting signal when the second magnetic contactor is closed; a third magnetic contactor side AND circuit which takes a logical AND of a preset opening / closing setting signal of the third magnetic contactor and an operation permission setting signal when the third magnetic contactor is closed; an operation permission setting side adder which adds up the numbers where the logical AND results of each of the first to third magnetic contactor side AND circuits are 1; a load connection permission determination processing section including a switching setting side adder which adds a certain number, a first comparator which outputs 1 only when the sum output of the operation permission setting side adder is equal to 1, a second comparator which outputs 1 only when the sum output of the switching setting side adder is equal to 1, a third comparator which outputs 1 when the absolute value of the difference between a voltage detection value which detects the voltage of the output filter capacitor and a voltage detection value which detects the voltage on the load side of the output side electromagnetic contactor is smaller than a set voltage determination level, and a load connection permission signal generating AND circuit which takes a logical AND of the outputs of the first to third comparators and outputs a signal which permits load connection when a logical AND condition is established; a second adder on the operation permission setting side that adds up the numbers of preset operation permission settings for the first electromagnetic contactor during output filter capacitor voltage control, operation permission settings for the second electromagnetic contactor during output filter capacitor voltage control, and operation permission settings for the third electromagnetic contactor during output filter capacitor voltage control, and a fourth comparator that outputs 1 only when the sum output of the second adder on the operation permission setting side is equal to 1; a first AND circuit which takes a logical AND of an open / close setting signal of the first electromagnetic contactor and a load connection permission signal, a second AND circuit which takes a logical AND of an open / close setting signal of the second electromagnetic contactor and a load connection permission signal, and a third AND circuit which takes a logical AND of an open / close setting signal of the third electromagnetic contactor and a load connection permission signal; a fourth AND circuit that takes a logical AND of a signal obtained by logically inverting the load connection permission signal, an output signal of the fourth comparator, and an operation permission signal in the first electromagnetic contactor during output filter capacitor voltage control; a fifth AND circuit that takes a logical AND of a signal obtained by logically inverting the load connection permission signal, an output signal of the fourth comparator, and an operation permission signal in the second electromagnetic contactor during output filter capacitor voltage control; a sixth AND circuit that takes a logical AND of a signal obtained by logically inverting the load connection permission signal, an output signal of the fourth comparator, and an operation permission signal in the third electromagnetic contactor during output filter capacitor voltage control; a first OR circuit that performs a logical OR process on the outputs of the first AND circuit and the fourth AND circuit and outputs an opening / closing command for the first electromagnetic contactor; a second OR circuit that performs a logical OR process on the outputs of the second AND circuit and the fifth AND circuit and outputs an opening / closing command for the second electromagnetic contactor; and a third OR circuit that performs a logical OR process on the outputs of the third AND circuit and the sixth AND circuit and outputs an opening / closing command for the third electromagnetic contactor. a first selection circuit which performs a logical OR operation on the outputs of the first, second and third AND circuits, and outputs 0 when the result is 0 and 1 when the result is 1; and a second selection circuit which performs a logical OR operation on the outputs of the fourth, fifth and sixth AND circuits, and outputs 0 when the result is 0 and 1 when the result is 1; an opening / closing command / current control permission signal generating unit having a current control permission signal generating adder that adds the outputs of the first selection circuit and the second selection circuit and outputs a current control permission signal of either current control non-permission, current control, or output filter capacitor voltage control according to a result of the addition; a first AND circuit that takes a logical AND of an opening / closing command for the first electromagnetic contactor output from the first OR circuit and an opening / closing state signal for the first electromagnetic contactor; a second AND circuit that takes a logical AND of an opening / closing command for the second electromagnetic contactor output from the second OR circuit and an opening / closing state signal for the second electromagnetic contactor; a third AND circuit that takes a logical AND of an opening / closing command for the third electromagnetic contactor output from the third OR circuit and an opening / closing state signal for the third electromagnetic contactor; an output side electromagnetic contactor opening / closing command generating unit including: a first selector that outputs 1 when the load connection permission signal is permission and 0 when the load connection permission signal is not permission; and a fourth AND circuit that takes a logical AND between the output signal of the first selector and a signal resulting from a logical OR process of the outputs of the first to third AND circuits, and outputs an output side electromagnetic contactor opening / closing command; a current range switching processing unit including a second selector that outputs 0 or 1 in response to an opening / closing command for the first electromagnetic contactor, outputs 0 or 2 in response to an opening / closing command for the second electromagnetic contactor, and outputs 0 or 3 in response to an opening / closing command for the third electromagnetic contactor, and an adder that adds up outputs of the second selector, and that selects one of the current detection values ​​of the first to third current detectors in response to an output of the adder; a current controller that generates a voltage command for the power conversion device by applying proportional control and integral control using set proportional gain and integral gain so that the current detection value selected by the current range switching processing unit becomes a set current command value when the current control permission signal generated by the opening / closing command / current control permission signal generation unit is current control, and generates a voltage command for the power conversion device by applying proportional control and integral control using set proportional gain and integral gain so that the current detection value selected by the current range switching processing unit becomes a set current command value when the current control permission signal is output filter capacitor voltage control, and switches the current command, and the proportional gain and integral gain to zero when the current control permission signal does not permit current control.

4. a first current detector on a front side of an output filter having a first current rating, a first reactor, a first electromagnetic contactor on a front side of the output filter for selecting the first current detector, a first electromagnetic contactor on a rear side of the output filter for selecting the first current detector on the rear side of the output filter, a first current detector on a rear side of the output filter having a first current rating, a fourth reactor, and an output side electromagnetic contactor; a series circuit including an output filter front-side second current detector having a second current rating smaller than the first current detector, a second reactor, and an output filter front-side second electromagnetic contactor that selects the second current detector, the series circuits being connected in parallel to the first reactor and the output filter front-side first electromagnetic contactor, respectively; and a series circuit including an output filter front-side third current detector having a third current rating smaller than the second current detector, a third reactor, and an output filter front-side third electromagnetic contactor that selects the third current detector. an output filter capacitor connected between a common connection point of the output filter front-side first electromagnetic contactor and the output filter rear-side first electromagnetic contactor and a negative terminal of a power conversion device; a series circuit connected in parallel between both ends of the first electromagnetic contactor on the rear side of the output filter, the series circuit being made up of a second current detector on the rear side of the output filter having a second current rating smaller than the first current detector and a second electromagnetic contactor on the rear side of the output filter selecting the second current detector, and a series circuit being made up of a third current detector on the rear side of the output filter having a third current rating smaller than the second current detector and a third electromagnetic contactor on the rear side of the output filter selecting the third current detector, A load connection permission determination processing unit and an opening / closing command / current control permission signal generating unit as described in claim 3, wherein an opening / closing setting of the first electromagnetic contactor used in the load connection permission determination processing unit is changed to an opening / closing setting of a first electromagnetic contactor on a front side of an output filter and a first electromagnetic contactor on a rear side of the output filter, an opening / closing setting of the second electromagnetic contactor is changed to an opening / closing setting of a second electromagnetic contactor on a front side of the output filter and a second electromagnetic contactor on a rear side of the output filter, and an opening / closing setting of the third electromagnetic contactor is changed to an opening / closing setting of a third electromagnetic contactor on the front side of the output filter and a third electromagnetic contactor on the rear side of the output filter, an operation permission setting signal when the first electromagnetic contactor is closed is changed to an operation permission setting signal when the first electromagnetic contactor on the front side of the output filter and the first electromagnetic contactor on the rear side of the output filter are closed, an operation permission setting signal when the second electromagnetic contactor is closed is changed to an operation permission setting signal when the second electromagnetic contactor on the front side of the output filter and the second electromagnetic contactor on the rear side of the output filter are closed, and an operation permission setting signal when the third electromagnetic contactor is closed is changed to an operation permission setting signal when the third electromagnetic contactor on the front side of the output filter and the third electromagnetic contactor on the rear side of the output filter are closed, an operation permission setting for the first electromagnetic contactor during the filter capacitor voltage control is changed to an operation permission setting for the first electromagnetic contactor on the front side of the output filter and the first electromagnetic contactor on the rear side of the output filter during the filter capacitor voltage control, an operation permission setting for the second electromagnetic contactor during the filter capacitor voltage control is changed to an operation permission setting for the second electromagnetic contactor on the front side of the output filter and the second electromagnetic contactor on the rear side of the output filter during the filter capacitor voltage control, and an operation permission setting for the third electromagnetic contactor during the filter capacitor voltage control is changed to an operation permission setting for the third electromagnetic contactor on the front side of the output filter and the third electromagnetic contactor on the rear side of the output filter during the filter capacitor voltage control, a load connection permission determination processing unit and an opening / closing command / current control permission signal generating unit configured such that an output of the first logical OR circuit is changed to output an opening / closing command for a first electromagnetic contactor on a front side of an output filter and a first electromagnetic contactor on a rear side of the output filter, an output of the second logical OR circuit is changed to output an opening / closing command for a second electromagnetic contactor on a front side of the output filter and a second electromagnetic contactor on a rear side of the output filter, and an output of the third logical OR circuit is changed to output an opening / closing command for a third electromagnetic contactor on a front side of the output filter and a third electromagnetic contactor on a rear side of the output filter; 4. The output side electromagnetic contactor opening / closing command generating unit according to claim 3, wherein the opening / closing command for the first electromagnetic contactor used in the output side electromagnetic contactor opening / closing command generating unit is changed to an opening / closing command for an output filter front side first electromagnetic contactor and an output filter rear side first electromagnetic contactor, and a status signal of the first electromagnetic contactor is changed to a status signal of the output filter front side first electromagnetic contactor and the output filter rear side first electromagnetic contactor, changing the opening / closing command for the second electromagnetic contactor to an opening / closing command for the second electromagnetic contactor on the front side of the output filter and the second electromagnetic contactor on the rear side of the output filter, and changing the status signal of the second electromagnetic contactor to a status signal for the second electromagnetic contactor on the front side of the output filter and the second electromagnetic contactor on the rear side of the output filter; an output side electromagnetic contactor opening / closing command generating unit configured to change the opening / closing command of the third electromagnetic contactor to an opening / closing command of an output filter front side third electromagnetic contactor and an output filter rear side third electromagnetic contactor, and to change a status signal of the third electromagnetic contactor to a status signal of the output filter front side third electromagnetic contactor and the output filter rear side third electromagnetic contactor; a current range switching processing unit including: a second selector that outputs 0 or 1 in response to an opening / closing command for a first electromagnetic contactor on a front side of an output filter and a first electromagnetic contactor on a rear side of an output filter, that outputs 0 or 2 in response to an opening / closing command for a second electromagnetic contactor on a front side of an output filter and a second electromagnetic contactor on a rear side of an output filter, and that outputs 0 or 3 in response to an opening / closing command for a third electromagnetic contactor on a front side of an output filter and a third electromagnetic contactor on a rear side of an output filter; an adder that adds up outputs of the second selector; an output filter front-side selector that selects a current detection value of one of the first to third current detectors on the front side of the output filter in response to an output of the adder; and an output filter rear-side selector that selects a current detection value of one of the first to third current detectors on the rear side of the output filter in response to an output of the adder; When the current control permission signal generated by the opening / closing command / current control permission signal generation unit is current control, proportional control is performed using a set proportional gain for current control so that the current detection value of the output filter front-side current detector selected by the output filter front-side selector becomes the set current command value; generating a voltage command for the power conversion device by performing integral control using an integral gain for current control that is set so that the current detection value of the output filter rear side current detector becomes a set current command value; a current controller that generates a voltage command for the power converter by performing proportional control and integral control using a proportional gain and an integral gain for output filter capacitor voltage control that are set so that a current detection value of an output filter front-side current detector selected by the output filter front-side selector becomes a current command value during the set output filter capacitor voltage control when the current control permission signal is output filter capacitor voltage control, and that switches the current command, the proportional gain, and the integral gain to zero when the current control permission signal does not permit current control.

5. The power conversion device according to claim 4, further comprising a current command enable / disable selection circuit which enables the current command on the input side of the current controller only when, when a current control permission signal specifying current control is output from the opening / closing command / current control permission signal generation unit, all of the output side electromagnetic contactors connected to the main circuits of all of the power conversion devices connected in parallel are in a closed state.

6. 6. The power conversion device according to claim 4 or 5, wherein an operation permission setting determination unit that counts the number of opening and closing of each electromagnetic contactor based on status signals of a first electromagnetic contactor on a front side of the output filter and a first electromagnetic contactor on a rear side of the output filter, status signals of a second electromagnetic contactor on a front side of the output filter and a second electromagnetic contactor on a rear side of the output filter, and status signals of a third electromagnetic contactor on a front side of the output filter and a third electromagnetic contactor on a rear side of the output filter is provided in accordance with the number of power conversion devices operating in parallel, and the operation permission setting determination unit is selected in accordance with the set number of parallel operation.

7. 6. The power conversion device according to claim 4 or 5, characterized in that a circuit between any one of the multiple power conversion devices and the load is enabled, and for circuits between the other power conversion devices and the load, the second current detector, the second reactor, the second electromagnetic contactor, the third current detector, the third reactor, and the third electromagnetic contactor are deleted, the current range switching processing unit is deleted, only the current detection value of the first current detector is used as a feedback input to the current controller, and an operation permission setting with the front-side second electromagnetic contactor and the rear-side second electromagnetic contactor of the output filter closed and an operation permission setting with the front-side third electromagnetic contactor and the rear-side third electromagnetic contactor of the output filter closed are not permitted.

8. a first carrier frequency selection unit which compares a rated current of the power conversion device with a rated current when the front-side first electromagnetic contactor and the rear-side first electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the first electromagnetic contactor is selected, a current obtained by dividing the rated current of the power conversion device by a first set number with the rated current when the front-side first electromagnetic contactor and the rear-side first electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the first electromagnetic contactor is selected with a current obtained by dividing the rated current of the power conversion device by a second set number with the rated current when the front-side first electromagnetic contactor and the rear-side first electromagnetic contactor of the output filter are selected, and selects one of first to third carrier frequencies which are set to be successively higher according to a total value of the comparison results in which the rated current is smaller when the first electromagnetic contactor is selected; a second carrier frequency selection unit which compares a rated current of the power conversion device with a rated current when the front-side second electromagnetic contactor and the rear-side second electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the second electromagnetic contactor is selected with a current obtained by dividing the rated current of the power conversion device by a first set number with the rated current when the front-side second electromagnetic contactor and the rear-side second electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the second electromagnetic contactor is selected with a current obtained by dividing the rated current of the power conversion device by a second set number with the rated current when the front-side second electromagnetic contactor and the rear-side second electromagnetic contactor of the output filter are selected, and selects one of first to third carrier frequencies which are set to be successively higher according to a total value of the comparison results in which the rated current is smaller when the second electromagnetic contactor is selected; a third carrier frequency selection unit which compares a rated current of the power conversion device with a rated current when the front-side third electromagnetic contactor and the rear-side third electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the third electromagnetic contactor is selected, a current obtained by dividing the rated current of the power conversion device by a first set number with the rated current when the front-side third electromagnetic contactor and the rear-side third electromagnetic contactor of the output filter are selected, and compares a comparison result in which the rated current is smaller when the third electromagnetic contactor is selected with a current obtained by dividing the rated current of the power conversion device by a second set number with the rated current when the front-side third electromagnetic contactor and the rear-side third electromagnetic contactor of the output filter are selected, and selects one of the first to third carrier frequencies which are set to be successively higher according to a total value of the comparison results in which the rated current is smaller when the third electromagnetic contactor is selected; a carrier frequency setting unit that sets the output of the first carrier frequency selection unit when a first electromagnetic contactor on a front side of the output filter and a first electromagnetic contactor on a rear side of the output filter are selected, that sets the output of the second carrier frequency selection unit when a second electromagnetic contactor on a front side of the output filter and a second electromagnetic contactor on a rear side of the output filter are selected, and that sets the output of the third carrier frequency selection unit when a third electromagnetic contactor on a front side of the output filter and a third electromagnetic contactor on a rear side of the output filter are selected.

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