Power conversion device

Abstract

Provided is a power conversion device in which the output ripple can be suppressed by performing operation in the appropriate number of parallel power conversion devices according to the magnitude of a current rating. A plurality of power conversion devices 1-N are provided in parallel with a load 200. A first current detector HCT_A11 having a first current rating, a first reactor L_A11, and an MC11 selecting the HCT_A11 are each inserted in an electric path connecting each power conversion device and the load and are sequentially connected in series from the power conversion device to the load. A series circuit comprising a second HCT_A21 having a small current rating, an L_A21, and an MC21 is connected between both ends of the MC11 in parallel as many as the number of installed power conversion devices. N devices are operated in parallel in a region where the operation of a plurality of devices having large current ratings are required, and the appropriate number of devices are operated in a small current region where operation is possible according to each current rating.

Description

Power Conversion Device

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

[0002] There is a demand for power conversion devices with large capacity and multiple current ratings. Therefore, 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 disclosed in Patent Document 1 has been proposed.

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

[0005] 1, an HCT1 (first current detector) and an electromagnetic contactor MC1 (hereinafter also referred to as MC) 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. An 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 the outputs of power conversion devices equipped with a plurality of HCTs having different current ratings to operate a plurality of devices at the same time.

[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 (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 a first electromagnetic contactor MC11, HCT_11, and reactor L11 that select a first current detector HCT_11 having a first current rating are connected in series in the electrical path connecting the power conversion device 1 and the load 200 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 the HCT_11 and a second electromagnetic contactor MC21 for selecting the HCT_21 are connected in series across the 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. 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. Power conversion devices 1 and 2 are also configured not to perform carrier synchronization. Current control commands are sent to each power conversion device from a command generation unit.

[0013] Japanese Patent Application Laid-Open No. 2021-180533

[0014] Figure 4 shows an example of an output current waveform in response to a current command. Here, the case is shown where the output MC of power conversion device 1 closes and then the MC of power conversion device 2 closes. The switching operation of the MC varies depending on the individual component. In large-capacity MCs, it can take tens to hundreds of milliseconds from the time the switching signal is input until the MC actually operates. Current cannot be output until the MC is closed. This means that the timing at which the output current of each paralleled device rises differs. 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 current waveforms of the output current and load current 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 devices, carrier ripple may occur equally between 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 devices occurs in the load current, the carrier ripple is larger than when operating with only one device.

[0016] The issues encountered when operating multiple units by simply combining outputs using prior art technology are summarized below. 1. There is no synchronization configuration for output current commands between parallel units, resulting in poor responsiveness to commands. 2. When operating multiple units, the output ripple of the power conversion device increases with the number of parallel units. This increases the ripple component of the output current, leading to increased harmonics and unintended losses on the load side. If a small output current is sufficient, operating only one unit can suppress the output ripple. 3. In configurations with an output filter, 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 account circuits with a current range switching switch and an output switch. As a result, depending on the opening and closing timing of the current range switching switch and the output switch, current control can cause the integral term of the current control to diverge, resulting in abnormal current control, an overcurrent failure, and the power conversion device can fail and shut down, preventing intended control.

[0017] The present invention is intended to solve the above-mentioned problems, and its object is to provide a power conversion device that can operate with an appropriate number of parallel units depending on the magnitude of the current rating and suppress output ripple.

[0018] In order to solve the above problem, a power conversion device according to a first aspect of the present invention provides a power conversion device including a plurality of power conversion devices connected in parallel to a load, 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 to the load and are connected in series in sequence from the power conversion device to the load, and 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 that takes the logical product 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 that takes the logical product 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 that receives as input the output of the first magnetic contactor-side AND circuit and the output of the second magnetic contactor-side AND circuit; a second exclusive OR circuit that receives as input the opening / closing setting signal of the first magnetic contactor and the opening / closing setting signal of the second magnetic contactor; and a load connection permission signal generating AND circuit that takes the logical product of the output of the first exclusive OR circuit and the output of the second exclusive OR circuit, and outputs a signal that 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 that 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, and outputs an opening / closing command for the first electromagnetic contactor; a second electromagnetic contactor opening / closing command generating AND circuit that 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, and outputs an opening / closing command for the second electromagnetic contactor; and a current control permission signal generating OR circuit that performs a logical OR operation 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, and generates a current control permission signal;the power converter comprises: 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 generation unit are input; a current range switching processing unit which has a logical AND circuit which takes the logical AND of the 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 according to the output of the logical AND circuit; and a current controller which, when the current control permission signal generated by the opening / closing command / current control permission signal generation unit permits control, performs 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, to generate a voltage command for the power conversion device, and when the current control permission signal does not permit control, switches the current command, proportional gain, and integral gain to zero.

[0019] The power conversion device according to claim 2 is the power conversion device according to claim 1, wherein the main circuit of the power conversion device is configured by connecting in parallel between both ends of the first electromagnetic contactor series circuits each consisting of the second current detector, the second reactor, and the second electromagnetic contactor, the number of which is equal to the number of installed power conversion devices; and the second electromagnetic contactor side AND circuit of the load connection permission determination processing unit has AND circuits for calculating the logical product of the open / close setting signal of the second electromagnetic contactor and the operation permission signal when the second electromagnetic contactor is closed, the number of which is 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 when 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, a switching setting side adder that adds up the number of times when the first electromagnetic contactor side AND signal and the second electromagnetic contactor side AND signal for the number of installed power conversion devices are closed, a first comparator that outputs 1 only when the added output of the operation permission setting side adder is equal to 1, a second comparator that outputs 1 only when the added output of the switching setting side adder is equal to 1, and a load connection permission signal generating AND circuit that takes the logical AND of the outputs of the first comparator and second comparator and outputs a signal that permits load connection when a logical 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 that take the logical product of the load connection permission signal and the 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 an OR circuit that performs logical OR processing of the 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 circuits, the number of which is equal to the number of installed power conversion devices; and the current range switching processing unit has, instead of the exclusive OR circuit, an adder that adds up the number of times 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 number of second electromagnetic contactors, the number of installed power conversion devices, depending on the addition result of the adder.

[0020] The power conversion device according to claim 3 is a plurality of power conversion devices are provided in parallel with a load, and a main circuit of the power conversion device is configured to include 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 conversion devices to the load and connected in series in sequence from the power conversion device 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, the 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, the 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 first electromagnetic contactor, the fourth reactor, and a negative terminal of the power conversion device; a first magnetic contactor side AND circuit that 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 that 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 that 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 that adds up the numbers where the logical AND results of the first to third magnetic contactor side AND circuits are 1; a load connection permission determination processing unit having a switching setting side adder that adds a certain number, a first comparator that outputs 1 only when the added output of the operation permission setting side adder is equal to 1, a second comparator that outputs 1 only when the added 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 the voltage detection value that detects the voltage of the output filter capacitor and the 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 the logical product of the outputs of the first to third comparators and outputs a signal that permits load connection when a logical product 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 magnetic contactor during output filter capacitor voltage control, the operation permission setting for the second magnetic contactor during output filter capacitor voltage control, and the operation permission setting for the third magnetic contactor during output filter capacitor voltage control; 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 that takes a logical AND of the opening / closing setting signal of the first magnetic contactor and the load connection permission signal; a second AND circuit that takes a logical AND of the opening / closing setting signal of the second magnetic contactor and the load connection permission signal; a third AND circuit that takes a logical AND of the opening / closing setting signal of the third magnetic contactor and the load connection permission signal; and a fourth AND circuit that takes a logical AND of a signal obtained by logically inverting the load connection permission signal, the output signal of the fourth comparator, and the operation permission signal of the first magnetic 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, the output signal of the fourth comparator, and the operation permission signal at the second electromagnetic contactor when controlling the output filter capacitor voltage; a sixth AND circuit that takes a logical AND of a signal obtained by logically inverting the load connection permission signal, the output signal of the fourth comparator, and the operation permission signal at the third electromagnetic contactor when controlling the output filter capacitor voltage; a first OR circuit that performs a logical OR operation on the outputs of the first AND circuit and the fourth AND circuit to output an opening and closing command for the first electromagnetic contactor; a second OR circuit that performs a logical OR operation on the outputs of the second AND circuit and the fifth AND circuit to output an opening and closing command for the second electromagnetic contactor; and a third OR circuit that performs a logical OR operation on the outputs of the third AND circuit and the sixth AND circuit to output an opening and closing command for the third electromagnetic contactor. a first selection circuit that 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 that 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 for current control non-permission, current control, or output filter capacitor voltage control depending on the addition result; a first AND circuit that takes the logical product of the first electromagnetic contactor switching command and the first electromagnetic contactor switching state signal output from the first OR circuit; a second AND circuit that takes the logical product of the second electromagnetic contactor switching command and the second electromagnetic contactor switching state signal output from the second OR circuit; and a third AND circuit that takes the logical product of the third electromagnetic contactor switching command and the third electromagnetic contactor switching state signal output from the third OR circuit. an output side electromagnetic contactor opening / closing command generating section having a first selector that outputs 1 when the load connection permission signal is permission and 0 when it is not permission, and a fourth AND circuit that takes a logical AND of the output signal of the first selector and a signal resulting from performing a logical OR process on the outputs of the first to third AND circuits, and outputs an output side electromagnetic contactor opening / closing command; a current range switching processing section having a second selector that outputs 0 or 1 in response to the opening / closing command for the first electromagnetic contactor, outputs 0 or 2 in response to the opening / closing command for the second electromagnetic contactor, and outputs 0 or 3 in response to the opening / closing command for the third electromagnetic contactor, and an adder that adds up the outputs of the second selector, and that selects a current detection value of one of the first to third current detectors in response to the output of the adder; When the current control permission signal generated by the opening / closing command / current control permission signal generation unit is for current control, proportional control and integral control are performed using set proportional gains and integral gains so that the current detection value selected by the current range switching processing unit becomes a set current command value, thereby generating a voltage command for the power conversion device; when the current control permission signal is for output filter capacitor voltage control, proportional control and integral control are performed using set proportional gains and integral gains so that the current detection value selected by the current range switching processing unit becomes a 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 does not permit current control, switching the current command, and the proportional gain and integral gain to zero.

[0021] The power conversion device according to claim 4 includes a plurality of power conversion devices provided in parallel with a load, and 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 a rear side of the output filter, a first current detector on a rear side of the output filter having the first current rating, a fourth reactor, and an output-side electromagnetic contactor, which are each inserted in an electric path connecting each of the power conversion devices to the load and are connected in series in sequence from the power conversion device to the load. a series circuit connected in parallel with the series circuit of the first reactor and the output filter front-side first electromagnetic contactor, the series circuit being composed of a second current detector on the output filter front side having a second current rating smaller than that of the first current detector, the second reactor, and the second electromagnetic contactor on the output filter front side that selects the second current detector, and a series circuit being composed of a third current detector on the output filter front side having a third current rating smaller than that of the second current detector, the third reactor, and the third electromagnetic contactor on the output filter front side that selects the third current detector; an output filter capacitor connected between a common connection point of the first electromagnetic contactor on the output filter front side and the first electromagnetic contactor on the output filter rear side and the negative terminal of the power conversion device; a series circuit connected in parallel between both ends of the first output filter rear-side electromagnetic contactor, the series circuit including a second output filter rear-side current detector having a second current rating smaller than that of the first current detector and a second output filter rear-side electromagnetic contactor that selects the second current detector, and a series circuit connected in parallel between both ends of the first output filter rear-side electromagnetic contactor, the series circuit including a third output filter rear-side current detector having a third current rating smaller than that of the second current detector and a third output filter rear-side electromagnetic contactor that selects the third current detector,The load connection permission determination processing unit and the opening / closing command / current control permission signal generating unit according to claim 3 change the opening / closing setting of the first electromagnetic contactor used in the load connection permission determination processing unit to the opening / closing setting 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, change the opening / closing setting of the second electromagnetic contactor to the opening / closing setting 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 change the opening / closing setting of the third electromagnetic contactor to the opening / closing setting 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, 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 a switching command / current control permission signal generating unit configured so that the output of the first OR circuit is changed to output 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, the output of the second OR circuit is changed to output 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 the output of the third OR circuit is changed to output 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; and an 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 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 and the status signal of the first electromagnetic contactor is changed to a status signal 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, an output side electromagnetic contactor opening / closing command generating unit configured to change 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 change 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, and change the opening / closing command for the third electromagnetic contactor to an opening / closing command 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, and change the status signal of the third electromagnetic contactor to a status signal 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;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, and 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 the 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 the output of the adder; and 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 a set current command value, The power converter is characterized in that it comprises a current controller which performs integral control using an integral gain for current control that is set so that the current detection value of the output filter rear current detector becomes a set current command value, thereby generating a voltage command for the power converter; when the current control permission signal is output filter capacitor voltage control, performs proportional control and integral control using a proportional gain and integral gain for output filter capacitor voltage control that are set so that the current detection value of the output filter front-side current detector selected by the output filter front-side selector becomes a set current command value for output filter capacitor voltage control, thereby generating a voltage command for the power converter; and when the current control permission signal is current control prohibition, switches the current command, proportional gain, and integral gain to zero.

[0022] The power conversion device according to claim 5 is the power conversion device according to claim 4, further comprising a current command enable / disable selection circuit that enables the current command on the input side of the current controller only when, when a current control enable signal specifying current control is output from the opening / closing command / current control enable 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 the closed state.

[0023] The power conversion device according to claim 6 is the power conversion device according to claim 4 or 5, 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 devices, and the operation permission setting determination unit counts the number of times each electromagnetic contactor is opened and closed 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, and determines an operation permission setting with the electromagnetic contactor closed to be used in the load connection permission determination processing unit for the electromagnetic contactor with the smallest number of times of opening and closing, and the operation permission setting determination unit is selected in accordance with the set number of parallel operation devices.

[0024] The power conversion device according to claim 7 is the power conversion device according to claim 4 or 5, wherein a circuit between any one of the plurality of power conversion devices and the 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, only the current detection value of the first current detector is used as feedback input to the current controller, and the setting to permit operation when the second electromagnetic contactor on the front side and the second electromagnetic contactor on the rear side of the output filter are closed and the setting to permit operation when the third electromagnetic contactor on the front side and the third electromagnetic contactor on the rear side of the output filter are closed are not permitted.

[0025] The power conversion device according to claim 8 is the power conversion device according to claim 4 or 5, further comprising: a first carrier frequency selection unit that 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, 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 set higher in frequency in accordance with the 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 that 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, 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, 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 set higher in frequency in accordance with the 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 that 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, 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 first to third carrier frequencies set higher in frequency in accordance with the 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.

[0026] (1) According to the inventions described in claims 1 to 8, it is possible to operate multiple units in parallel in areas where multiple units with high current ratings are required, and to operate an appropriate number of units according to the current rating in areas where the operable current is low. This reduces carrier ripple, thereby reducing harmonics caused by carriers. (2) According to the invention described in claim 3, a device having a filter capacitor on the output side of a power conversion device can achieve the same effect as described in (1). (3) According to the invention described in claim 4, a device having a filter capacitor on the output side of a power conversion device and reactors on both the front and rear sides thereof to form an LCL-type filter can achieve the same effect as described in (1). (4) According to the invention described in claim 5, it is possible to increase the response speed of the output current when the response speed is defined by the time it takes for the output current to reach the target current after a change in command value. (5) According to the invention described in claim 6, the number of opening and closing operations of each electromagnetic contactor is determined, thereby uniforming the number of opening and closing operations, thereby extending the life of the device. (6) According to the invention described in claim 7, it is possible to reduce the number of parts by removing 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 due to sudden changes in current.

[0027] 1 is a configuration diagram showing an example of a prior art power conversion device equipped with multiple HCTs with different current ratings. FIG. 1 is a configuration diagram when the outputs of prior art power conversion devices are combined to operate multiple power conversion devices. FIG. 2 is a control configuration diagram when prior art power conversion devices are combined. FIG. 3 is an output current waveform diagram in response to a current command in the control of FIG. 3. FIG. 4 is a current waveform diagram of each part in the control of FIG. 3. FIG. 4 is a main circuit configuration diagram of a power conversion device according to a first embodiment of the present invention. FIG. 5 is an HCT selection MC switching control configuration diagram of the first embodiment of the present invention. FIG. 6 is a basic control configuration diagram of a power conversion device according to the second embodiment of the present invention. FIG. 7 is a main circuit configuration diagram of a power conversion device according to a third embodiment of the present invention. FIG. 8 is an HCT selection MC switching control configuration diagram of the third embodiment of the present invention. FIG. 9 is an output MC switching control configuration diagram of the third embodiment of the present invention. FIG. 10 is a basic control configuration diagram of a power conversion device according to the third embodiment of the present invention. FIG. 11 is a main circuit configuration diagram of a power conversion device according to a fourth embodiment of the present invention. FIG. 12 is an HCT selection MC switching control configuration diagram of the fourth embodiment of the present invention. FIG. 13 is an output MC switching control configuration diagram of the fourth embodiment of the present invention. FIG. 10 is a basic control configuration diagram of a power conversion device according to a fourth embodiment of the present invention. FIG. 11 is a basic control configuration diagram of a power conversion device according to a fifth embodiment of the present invention. FIG. 12 is an output current waveform diagram when a current command is received and current control is performed before all output MCs are turned on. FIG. 13 is an output current waveform diagram when the control of the fifth embodiment of the present invention is performed. FIG. 14 is a configuration diagram for processing the number of opening and closing times of each MC according to a sixth embodiment of the present invention. FIG. 15 is an operation permission setting configuration diagram when each MC is closed according to the sixth embodiment of the present invention. FIG. 16 is an operation permission setting configuration diagram when the number of parallel units is 1 according to the sixth embodiment of the present invention. FIG. 17 is an operation permission setting configuration diagram when the number of parallel units is 2 according to the sixth embodiment of the present invention. FIG. 18 is an operation permission setting configuration diagram when the number of parallel units is 3 according to the sixth embodiment of the present invention. FIG. 19 is a main circuit configuration diagram of a power conversion device according to a seventh embodiment of the present invention. FIG. 19 is a carrier frequency selection configuration diagram when the first electromagnetic contactor is selected according to an eighth embodiment of the present invention. FIG. 19 is a carrier frequency setting configuration diagram according to the eighth embodiment of the present invention.

[0028] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. 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. It is not limited to power conversion devices with flying capacitors. Under the above prerequisites, it is necessary to develop a parallel operation method for multiple power conversion devices with multiple current ratings while achieving parallel operation, improving control accuracy, and preventing an increase in carrier ripple.

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

[0031] In Figure 6, multiple power conversion devices 1 and 2 are provided in parallel with a load 200, and in the electrical path 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 both ends of 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, except that the suffixes at the end of HCT_A, L_A, and MC are 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 the MC and the selection of the HCT are defined in Table 1.

[0034]

[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 configuration diagram of the HCT selection MC switching control. 10 is a load connection permission determination processing unit, and 20 is a switching command / current control permission signal generation unit. 11 is a first magnetic contactor-side logical product circuit that takes the logical product of a preset switching setting signal for the first magnetic contactor MC11 and an operation permission setting signal when the first magnetic contactor MC11 is closed. 12 is a second magnetic contactor-side logical product circuit that takes the logical product of a preset switching setting signal for 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 which receives 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 which receives 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] Reference numeral 15 denotes a logical product circuit for generating a load connection permission signal, which takes the logical product 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 product condition is met.

[0039] 16 is a logical product circuit for generating a first electromagnetic contactor opening / closing command, which takes the logical product 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] 17 is a logical product circuit for generating a second electromagnetic contactor opening / closing command, which takes the logical product of the load connection permission signal output from the load connection permission determination processing unit 10 and the opening / closing setting signal of the second electromagnetic contactor MC21, and outputs an opening / closing command for the second electromagnetic contactor MC21.

[0041] Reference numeral 18 denotes a logical sum circuit for generating a current control permission signal, which performs logical sum processing on the output of the logical sum circuit 16 for generating the first electromagnetic contactor opening / closing command and the output of the logical sum 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] 8, reference numeral 30 denotes 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 MC21 closing 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 the 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 not permitted 0.

[0045] When the current control permission signal indicates that control is permitted, 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 that control is not permitted, switches the current command, proportional gain, and integral gain 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 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 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]

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

[0051]

[0052] By performing this process, it becomes possible to select the appropriate relationship between HCT and MC selection. Furthermore, when there is no selection and 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 its 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 detected current value is 0. Therefore, when 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 malfunction. As a result, an overcurrent fault or the like occurs, causing the device to malfunction and shut down. When the current control permission signal is 0, the current command and current control proportional gain are set to 0, and the integral action is stopped by setting the integral term initial value. When both MC11 and MC21 are open, the integral term stops, so the current control does not malfunction. When the MC to be operated is commanded to close, the current control permission signal becomes 1, causing the current control to operate normally.

[0054] For example, power conversion device 1 is set to be permitted to operate with MC11 and MC21, and power conversion device 2 is set to be permitted to operate with MC12 but not with MC22. In this case, each control operates as described above, so when the current rating is large, both power conversion devices 1 and 2 are operated, and when the current rating is small, only power conversion device 1 is allowed to operate.

[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 only one unit is possible. This reduces the carrier ripple, thereby reducing harmonics caused by the carrier.

[0056] Fig. 9 shows a basic circuit configuration diagram of a power conversion device in Example 2. Fig. 9 differs from Fig. 6 of Example 1 in that N power conversion devices 1 to N are provided for 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 connected in parallel across both ends of the first electromagnetic contactor MC11 are connected in parallel by the number of the installed power conversion devices; other parts are configured in the same way as 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 the MC and the selection of the HCT are defined in Table 4.

[0058]

[0059] Table 4 shows the case of power conversion device 1, but the same applies to power conversion device 2, except that the subscript is changed to 2, and to power conversion device N, except that the subscript is changed to N. Figure 10 shows the configuration diagram of the HCT selection MC switching control.

[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 open / close setting signal for 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 open / close setting signal for 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 open / close setting signal for 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 AND circuit 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 the number when the selection result of selectors 52a to 52n is 1.

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

[0063] Reference numeral 55 denotes a switching setting side adder that adds the number of the selection results of the selectors 54a to 54n that are 1.

[0064] Reference numeral 56 denotes a comparator that 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 that outputs 1 only when the sum output of the opening / closing setting side adder 55 is equal to 1.

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

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

[0067] Similarly, N logical product circuits 59 are provided, and 59n is a logical product circuit that 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 operation on the outputs of the logical product circuits 59a to 59n and outputs a current control permission signal.

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

[0070] In Figure 10, the load connection permission determination process performs the following processes: (1) A logical AND is taken between the open / close setting of each MC and the closed operation permission setting (51a to 51n). If the result of the logical AND is 0, 0 is output; if it is 1, 1 is output. The outputs for all MCs are added together, the result is compared to 1, and 1 is output if they are equal, or 0 if they are not equal. (2) If the MC open / close setting is 0, 0 is output; if it is 1, 1 is output; and the results for all MCs are added together (55). The result is compared to 1, and 1 is output if they are equal, or 0 if they are not equal. (3) A logical AND is taken between the results of (1) and (2) to generate a load connection permission signal (58). A logical AND is taken between the load connection permission signal and the MC open / close setting to generate each MC open / close command (59a to 59n). The logical OR of these MC open / close commands is used as a current control permission signal (60).

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

[0072] An adder 72 adds the outputs of the selectors 71a to 71n (adds the number that is a close command). A current detection value setter 73 sets 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 its input side in the second embodiment are configured in the same manner as in the first embodiment shown in FIG.

[0074] FIG. 11 shows only one power conversion device. Other power conversion devices may have a similar configuration. The current controller 40 has a configuration 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 has an initial value set. 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 / closing command is output, and the corresponding number is set, thereby appropriately setting the HCT current detection value. For example, if the MC11 opening / closing command is 1, 1 is output; if the MC21 opening / closing command is 1, 2 is output; and if the MCN1 opening / closing command is 1, N is output. The output results are added by an adder 72. If the sum 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 connection permission determination process in the second embodiment.

[0077]

[0078]

[0079]

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

[0081] Furthermore, the switching command for 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 either 0 or 1, depending on the operation permission setting and the MC switching setting. Since the current control permission signal performs logical OR processing on each MC switching command, it is also clear that the signal becomes 1 only when any of the MC switching commands becomes 1. Note that other parts are configured in the same way as in Example 1.

[0082] The action and operation of the control configuration will be explained. 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 detected current value is selected accordingly. For example, if the MC11 switching command is 1, 1 is selected and the detected current value of HCT_A11 is selected. Similarly, if the MC21 switching command is 1, 2 is selected and the detected current value of HCT_A21 is selected, and if the MCN1 switching command is 1, N is selected and the detected current 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 allow operation with MC11, MC21, and MCN1, power conversion device 2 is set to allow operation with MC12 and MC22, and power conversion device N is set to allow operation with MCN1. In this case, each control operates as described above, so when the current rating is large, operation is performed with power conversion devices 1, 2, and N, when the current rating is next small, 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, the configuration is applicable not only to two-unit parallel connection but also to a parallel device with multiple units from 2 to N units, so that in areas where multiple units with large current ratings are required to be operated, it is possible to operate N units in parallel. In operating areas where the operable current is small according to each current rating, it is possible to operate an appropriate number of units, which reduces carrier ripple and therefore harmonics caused by the carrier.

[0086] FIG. 12 shows a main circuit configuration diagram of a power conversion device according to a third embodiment. In the third embodiment, the current rating is three, so the number of HCTs and MCs per unit is three. The number of power conversion devices connected in parallel is also three. However, as in the second embodiment, 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 embodiment is intended to include a capacitor at the output. In this example, the output filter is in the form of an LCL. Furthermore, a switch for disconnecting the load is provided after the L in the final stage of the LCL.

[0087] In Figure 12, three power conversion devices 1, 2, and 3 are provided for load 200, and in the electrical path connecting power conversion device 1 and 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 power conversion device 1 to load 200.

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

[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 and 3 and the loads are configured in the same manner as above, except that the suffixes at the end of each part are changed from 1 to 2 and 3, respectively.

[0091] In FIG. 13, reference numeral 80 denotes a load connection permission determination processing unit that determines whether to permit or prohibit the load connection, and is configured as follows.

[0092] Reference numeral 81 denotes a logical product circuit that takes the logical product 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 product circuit that calculates the logical product of a preset open / close setting signal for MC_A 21 and a setting signal for permitting operation with MC_A 21 closed.

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

[0095] Numerals 84 to 86 are selectors that select 0 when the output of each of the logical product circuits 81 to 83 is 0, and select 1 when the output is 1, and 87 is an operation permission setting side adder that adds the number when the selection result of the selectors 84 to 86 is 1.

[0096] Numerals 88 to 90 are selectors that 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 that adds the number when the selection result of selectors 88 to 90 is 1.

[0097] Reference numeral 92 denotes a comparator that outputs 1 only when the sum output of the operation permission setting side adder 87 is equal to 1, and reference numeral 93 denotes a comparator that outputs 1 only when the sum output of the opening / closing setting side adder 91 is equal to 1.

[0098] Reference numeral 94 denotes a subtractor that calculates 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 calculates the absolute value of the difference output from the subtractor 94.

[0099] A comparator 96 outputs 1 when the absolute value of the absolute value processor 95 is smaller than a set voltage determination level.

[0100] Reference numeral 97 denotes a load connection permission signal generating AND circuit that takes the logical AND of the outputs of comparators 92, 93, and 96, and outputs a load connection permission signal that specifies 1 for permission when the logical AND condition is satisfied and 0 for prohibition when the logical AND condition is not satisfied. Reference numeral 98 denotes a selector that selects 0 when the operation permission setting signal for the first electromagnetic contactor MC_A11 during filter capacitor voltage control is prohibitive and 1 when it is permitting. Reference numeral 99 denotes a selector that selects 0 when the operation permission setting signal for the second electromagnetic contactor MC_A21 during filter capacitor voltage control is prohibitive and 1 when it is permitting. Reference numeral 100 denotes a selector that selects 0 when the operation permission setting signal for the third electromagnetic contactor MC_A31 during filter capacitor voltage control is prohibitive and 1 when it is permitting. Reference numeral 101 denotes a second adder on the operation permission setting side that adds up the numbers for which the selection results of the selectors 98 to 100 are 1, and 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 that takes the logical AND of the load connection permission signal output from the logical AND circuit 97 and the switching setting signal of the MC_A11, 104 denotes a logical AND circuit that takes the logical AND of the load connection permission signal output from the logical AND circuit 97 and the switching setting signal of the MC_A21, and 105 denotes a logical AND circuit that takes the logical AND of the load connection permission signal output from the logical AND circuit 97 and the switching setting signal of the MC_A31.

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

[0102] Reference numeral 111 denotes a logical product circuit that takes the logical product 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 product circuit that takes the logical product of the output of the NOT circuit 108, the output of the comparator 102, and the operation permission setting signal in MC_A 31 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 product circuit 103 and the logical product circuit 110 and outputs an opening / closing command for the first electromagnetic contactor MC_A11.

[0105] Reference numeral 114 denotes a logical sum circuit that 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] A first selection circuit 116 performs a logical OR operation on the outputs of the AND circuits 103 to 105, and outputs 0 when the result is 0, and 1 when the result is 1.

[0108] A second selection circuit 117 performs a logical OR operation on the outputs of the AND circuits 110 to 112, and outputs 0 when the result is 0, and 2 when the result is 1.

[0109] Reference numeral 118 denotes 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 for disallowing current control, controlling current, or controlling the output filter capacitor voltage depending on the addition result. Note that the circuits from selectors 98 to 100 to the adder 118 constitute an opening / closing command / current control permission signal generating unit 119. While Fig. 13 shows a configuration diagram of power conversion device 1, power conversion devices 2 and 3 may also have a similar configuration.

[0110] In FIG. 13, the following configuration is different from that of the second embodiment. The rest of the configuration is 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 determination level, it is set to 1; if it is larger, it is set to 0 (94-96). (2) The result of (1) is added as one of the AND conditions in the load connection permission signal generation process of the second embodiment (97). (3) An MC operation permission setting during voltage control to equalize the filter capacitor voltage with the load voltage is added. (4) The MC operation permission setting during filter capacitor voltage control is set to 0 if it is 0, or 1 if it is 1. The outputs of the operation permission settings for each MC are added, and if the result is 1, it is set to 1; otherwise, it is set to 0 (98-102). (5) A logical product is calculated for the signal (3), the signal (4), and the logically inverted signal of the load connection permission signal (110-112). (6) A configuration (117) for calculating the logical sum of the results of (5) for each MC, and setting it to 0 if it is 0, and 2 if it is 1. (7) A configuration (116) for calculating the logical sum of the opening and closing commands of each MC, as in the second embodiment, and setting it to 0 if it is 0, and 1 if it is 1. (8) A configuration (118) for performing addition processing on the results of (6) and (7) and setting the result 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 product circuit 121 takes the logical product of the switching command of MC_A11 output from the logical sum circuit 113 in Fig. 13 and the status signal of MC_A11. A logical product circuit 122 takes the logical product of the switching command of MC_A21 and the status signal of MC_A21. A logical product circuit 123 takes the logical product 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 "disallow 0", an MC_C11 open command 0 is selected by a selector 125, and when the load connection permission signal is "allow 1", an MC_C11 close command 1 is selected by a selector 125.

[0113] A logical product of the outputs of the logical sum circuit 124 and the selector 125 is taken by a logical product circuit 126, and an MC_C11 opening / closing command is output.

[0114] In Fig. 14, (1) a logical product is taken of the switching command of the MC that selects the current rating and the status signal (121 to 123). (2) A logical sum is taken for the result of (1) in each MC (124). (3) An MC_C11 open command is issued when the load connection permission signal is 0, and an MC_C11 close command is issued when the load connection permission signal is 1 (125). (4) A logical product is taken of (2) and (3) (126) to be used as the MC_C11 switching command.

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

[0116] An adder 134 adds (adds the number that is a close command) the outputs of the selectors 131 to 133. A current detection value setter 135 sets 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 according to the output of the adder 134.

[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: current control is not permitted, 1: current command 1 is selected in the case of current control, or 2: output current command 2 during filter capacitor voltage control in the case of filter capacitor voltage control.

[0118] When the current control permission signal is current control 1, the current controller 140 generates a voltage command for the power conversion device by performing 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, and when the current control permission signal is output filter capacitor voltage control 2, the current controller 140 generates a voltage command for the power conversion device by performing 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, and when the current control permission signal is current control non-permission 0, the current command, proportional gain, and integral gain are switched to zero. Reference numeral 42 denotes a delay unit, and 43 denotes a limiter.

[0119] In 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 the main circuit is connected to the load 200, the following situations will occur. 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, which may cause an abnormal current to flow in components connected between the output filter capacitors and the load, which may damage the components.

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

[0121]

[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 for confirming 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 less than the voltage determination level and the load connection permission signal in Example 2 is 1, the load connection permission signal in Example 3 is 1. As a result, by using the load connection permission signal of this example, it is possible to avoid the above-mentioned states (1) and (2).

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

[0125]

[0126]

[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 under filter capacitor voltage control becomes 1. Also, in Table 10, when the load connection permission signal is 1, the current control permission signal becomes 1 if any of the MC opening and closing commands becomes 1. 1 means that current control is permitted. When the load connection permission signal is 0, the signal becomes 2 if any of the MC opening and closing commands becomes 1. 2 means that current control for output filter capacitor voltage control is permitted. In all other cases, the signal becomes 0. 0 means that current control is not permitted.

[0128] It can be seen 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 seen that the current control permission signal is 0 or 1.

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

[0130]

[0131] Each MC switching command is processed exclusively by the HCT selection MC switching control, so two or more signals will never be 1 at the same time. It can be seen that MC_C11 becomes 1 only when the load connection permission signal is 1, the switching command of each MC is 1, and the status signal is also 1. This means that the output MC will operate and connect to the load after the HCT selection is properly made.

[0132] Next, the function and operation of the control configuration will be described. The current range switching process is unchanged from the second embodiment. The operation when the current control permission signal is 0 or 1 is unchanged from the second embodiment. The operation differs when the current control permission signal is 2.

[0133] The 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 previous value of the integral term is fed back.

[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, each control operates as described above, so 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 power conversion device 1 alone, 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 a 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 a region where multiple units with a large current rating are required to be operated, multiple units can be operated in parallel. In an 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, thereby reducing harmonics caused by the carrier.

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

[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 that of 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 that of 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] Across both ends of MC_B11, a series circuit consisting of a second current detector HCT_B21 and MC_B21 on the post-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 post-side of the output filter having a third current rating are connected in parallel.

[0140] The circuits between the power conversion devices 2 and 3 and the load 200 are configured in the same manner as above, except that the last digits of the respective parts are changed from 1 to 2 and 3.

[0141] In Figure 16, the current rating is three and the number of paralleled power conversion devices is three. However, as with Example 2, the number of HCTs and MCs per device and the number of paralleled power conversion devices can be up to N. The main circuit configuration diagram has the following features: (1) HCTs are provided before and after the output filter. HCT_A is before the filter and HCT_B is after the filter. (2) The combinations of current rating, HCT, and MC are defined as shown in Table 12.

[0142]

[0143] Table 12 shows the values ​​for 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 an 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 components as those in FIG. 13 are designated by the same reference numerals. In FIG. 17, the following configuration differs from that in the third embodiment. Other components are the same. Here, the configuration diagram of power conversion device 1 is shown, but power conversion devices 2 and 3 may have a similar configuration. (1) The open / closed setting, the closed operation permission setting, the filter capacitor voltage control operation permission setting, and the opening / closing command for MC_A11 are changed to MC_A11 and MC_B11. (2) The open / closed setting, the closed operation permission setting, the filter capacitor voltage control operation permission setting, and the opening / closing command for MC_A21 are changed to MC_A21 and MC_B21. (3) The open / closed setting, the closed operation permission setting, the filter capacitor voltage control operation permission setting, and the opening / closing command for MC_A31 are changed to MC_A31 and MC_B31.

[0146] Figure 18 shows the output MC switching control configuration. In Figure 18, the same parts as in Figure 14 are designated by the same reference numerals. In Figure 18, the changes from Example 3 are as follows: (1) The switching command and status signal for MC_A11 are changed to MC_A11 and MC_B11. (2) The switching command and status signal for MC_A21 are changed to MC_A21 and MC_B21. (3) The switching command and status signal for MC_A31 are changed to MC_A31 and MC_B31.

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

[0148] Reference numeral 151 denotes a selector that 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 that 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 that 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 the current detection values ​​of the output filter front-side current detectors HCT_A11, HCT_A21, and HCT_A31 according to the output of the adder 154.

[0150] Reference numeral 156 denotes an output filter post-side selector that selects the current detection values ​​of the output filter post-side current detectors HCT_B11, HCT_B21, and HCT_B31 according 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 the current controller 158 .

[0152] The output (current detection value) side of the output filter rear side selector 156 is connected to the 1 side terminal of a selector 157 that switches the current detection value in accordance with 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 on the integral control side of the current controller 158 .

[0154] The current controller 158 in the fourth embodiment operates as follows: when the current control permission signal is for 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 155 becomes a set current command value, and integral control is performed using 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 for output filter capacitor voltage control, proportional control and integral control are performed using the 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 a 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 for current control prohibition, the current command, proportional gain, and 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 and integral gains of the current control are set to 0. (2) The feedback signals used for the proportional control and the 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 the integral control of the current control is switched depending on the current control permission signal. When the current control permission signal is 0 or 2, the feedback signal is HCT_A11, HCT_A21, or HCT_A31. When the current control permission signal is 1, the feedback signal is HCT_B11, HCT_B21, or HCT_B31.

[0156] Although this is HCT selection MC switching control, the basic operation is the same as in Example 3. The following changes are made from Example 3: Simultaneously with MC_A11, MC_A21, and MC_A31, MCs with the rating combinations shown in Table 12 are switched.

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

[0158] Although this is 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 properly performed, making it possible to connect to the load.

[0159] The operation of current control will be explained below. The current control will be explained. Proportional control is the dominant control in order to speed up the 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 which can accurately detect low-frequency regions, is set as the feedback signal. This makes it possible to achieve high-response, high-precision 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 current control accuracy, in regions where multiple units with a large current rating are required to be operated in parallel, multiple units can be operated in parallel. In operating regions where the operable current is small according to each current rating, an appropriate number of units can be operated. This reduces carrier ripple, thereby reducing harmonics caused by the carrier.

[0161] In the fifth embodiment, the configuration of the main circuit between the multiple power conversion devices and the 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. Figure 20 shows a basic control configuration diagram of the power conversion device in the fifth embodiment.

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

[0163] Reference numeral 161 denotes a logical product circuit which takes the logical product 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 product circuit 161 is 0 and selects a current command when the output is 1, and the output side of selector 162 is connected to the 1 side terminal of selector 136. Other parts are configured in the same way as in FIG. 19.

[0164] The switching operation of output MCs varies depending on the component. Large-capacity MCs can take tens to hundreds of milliseconds from the input of a switching signal until they actually operate. Therefore, unless a current command is received after all output MCs are turned ON, the timing at which the output current of each paralleled device rises will differ. This creates a problem: it takes a long time for the total output current to reach the command value. Figure 21 shows the current waveform when not all output MCs are turned ON. Here, the case is shown in which the output MC of power conversion device 1 is turned ON, followed by the output MC of power conversion device 3, and finally the output MC of power conversion device 2.

[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.

[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 remain unchanged from the fifth embodiment. A new process has been added to determine the operation permission setting for each MC closed in the HCT selection MC switching control. 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 operations for the MCs between parallel devices can be made uniform. Figure 23 shows a configuration diagram for processing the number of switching operations 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] Counter 166a counts the number of times that selector 165a outputs one signal and outputs the number of times that MC_A11 and MC_B11 open and close, counter 166b counts the number of times that selector 165b outputs one signal and outputs the number of times that MC_A12 and MC_B12 open and close, and counter 166c counts the number of times that 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 MC status signal. If the status signal is 0, counting is not performed, and if the status signal is 1, the count is incremented by one. Fig. 24 shows the configuration for setting operation permission when each MC is closed. The configuration is such that a selector 167 selects an operation permission setting according to the number of parallel units set when the MC is closed, and outputs the operation permission setting for each MC. Since the maximum number of units in parallel operation is three, selection is made according to whether there is one, two, or three units.

[0171] Figure 25 shows the operation permission setting for one parallel unit. For the MCs in parallel, the number of opening and closing times is compared, and the MC with the smallest number is set to 1 for closed operation permission setting. For MCs other than the smallest number of opening and closing times, the closed operation permission setting is set to 0. Furthermore, when the number of opening and closing times is the same, priority is given to those with a closed operation permission setting of 1, so that no more MCs than the number of units are turned on.

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

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

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

[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 in accordance with the selected output of the selector 173a.

[0177] Reference numeral 175 denotes a logical OR circuit that performs logical OR processing of 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 selected output of the selector 173a becomes an operation permission setting signal when MC_A11 and MC_B11 are closed, the selected output of the selector 174 becomes an operation permission setting signal when MC_A12 and MC_B12 are closed, and the selected 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. The MCs in parallel are compared for the number of opening and closing times, and the MC with the smallest number and the second smallest number of opening and closing times are set to 1 for closed operation permission setting. The MC with the most opening and closing times is set to 0 for closed operation permission setting. In addition, when the opening and closing times are the same, priority is given to those with a closed operation permission setting of 1, 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 times that MC_A11 and MC_B11 open and close with the number of times that MC_A12 and MC_B12 open and close, and 178 is a selector that selects either the number of times that MC_A11 and MC_B11 open and close (1) or the number of times that MC_A12 and MC_B12 open and close (0) depending on the comparison result of comparator 177.

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

[0183] A selector 181 selects the number of times MC_A11 and MC_B11 are switched (0) or the number of times MC_A12 and MC_B12 are switched (1) according to the comparison result of the comparator 177 .

[0184] Reference numeral 182 denotes a determiner that determines 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 determines 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 times MC_A11 and MC_B11 are opened and closed is equal to the selection output of the selector 180, 184b is a determinator that determines whether the number of times MC_A11 and MC_B11 are opened and closed is equal to the selection output of the selector 180, and 184c is a determinator that determines whether the number of times MC_A12 and MC_B12 are opened and closed is equal to the selection output of the selector 180.

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

[0187] 187a is a selector that selects 0 or 1 according to the output of the logical sum circuit 185, 187b is a selector that selects 0 or 1 according to the output of the logical sum circuit 186, and 187c is a selector that selects 0 or 1 according to the decision output of the decider 184c.

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

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

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

[0191] The operation permission setting for each MC closed will be explained. The process for equalizing the number of switching operations differs depending on the number of parallel units. In the case of a 3-parallel configuration, if the number of parallel units is 1, the number of switching operations can be equalized by always selecting the MC with the smallest number of switching operations. If the number of parallel units is 2, the number of switching operations can be equalized by selecting the MC with the smallest or second-largest number of switching operations. If the number of parallel units is 3, there is no imbalance in the number of switching operations between the devices, so no special process is required to equalize the number of switching operations. In this way, the MC operation permission setting differs to equalize the number of parallel units. With the configuration shown in Figure 24, the operation permission setting process 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 setting when the number of parallel units is 1 will be described. In Figure 25, first, the switching counts of MC_A11 and MC_B11 are compared with those of MC_A12 and MC_B12. The switching count of the MC with the lowest number of switching counts is then compared with those of MC_A13 and MC_B13. The MC with the lowest number of switching counts from this comparison becomes the MC with the lowest number of switching counts. The operation permission setting in closed state for the MC with the lowest number of switching counts is set to 1. The operation permission setting in closed state for the other MCs is set to 0. If the switching counts are equal, the operation permission settings are prioritized. In this example, the priority is highest for MC_A11 and MC_B11, MC_A12 and MC_B12, and MC_A13 and MC_B13.

[0193] Table 13 shows an example of the number of parallel connections before and after the change in the number of switching operations when one unit is connected in parallel.

[0194]

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

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

[0197]

[0198] An explanation will be given of the operation permission setting 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 is set to 1 when MC_A11 and MC_B11, MC_A12 and MC_B12, and MC_A13 and MC_B13 are closed.

[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.

[0200] The main circuit configuration of this embodiment is shown in Fig. 28. In this embodiment, three devices are connected in parallel, and no current range switching circuit is 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 designated by the same reference numerals. Fig. 28 differs from Fig. 16 in that HCT_A21, HCT_A31, L_A21, L_A31, MC_A21, MC_A31, MC_B21, MC_B31, HCT_B21, and HCT_B31 are deleted between power conversion devices 2 and 3 and load 200, the current range switching processing unit is deleted in power conversion devices 2 and 3, and the feedback input to the current controller is limited to the current detection value of the first current detector; other parts are configured the same as in Fig. 16. There are no other changes from embodiment 5 regarding the HCT selection MC opening and closing control, output MC opening and closing control, and control configuration.

[0202] In Figure 28, when the current rating is medium or small, if it is smaller than the rated current of one power conversion device, parallel operation is not necessary. In this case, driving a single device reduces carrier ripple, improving control accuracy. 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 by setting the operation permission setting for the MCs (MC_A21, MC_A31, MC_B21, MC_B31) when selecting medium or small current ratings in the HCT selection MC opening and closing control to not permit.

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

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

[0205] In Figure 29, 191 is a comparator that compares the rated current of the power conversion device with the rated current when the front-side first electromagnetic contactor MC_A11 and the rear-side 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] 194a is a selector that 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 0 if it is larger; 194b is a selector that 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 0 if it is larger; and 194c is a selector that 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 0 if it is larger.

[0207] Reference numeral 195 denotes an adder that adds the selected outputs of the selectors 194a to 194c, and 196 denotes a selector that selects carrier frequency 1 when the added output of adder 195 is 0 or 1, selects carrier frequency 2 that is higher than carrier frequency 1 when the added output is 3, and selects carrier frequency 3 that is higher than carrier frequency 2 when the added output is 7. The selected 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 conversion device is compared with the rated current when MC_A11 and MC_B11 are selected. If the rated current when MC_A11 and MC_B11 are selected is small, 1 is selected; if it is large, 0 is selected. Half the rated current of the power conversion device is compared with the rated current when MC_A11 and MC_B11 are selected. If the rated current when MC_A11 and MC_B11 are selected is small, 2 is selected; if it is large, 0 is selected. One-third the rated current of the power conversion device is compared with the rated current when MC_A11 and MC_B11 are selected. If the rated current when MC_A11 and MC_B11 are selected is small, 4 is selected; if it is large, 0 is selected. Each comparison result is added, and if the addition result is 0 or 1, carrier frequency 1 is set; if it is 3, carrier frequency 2; if it is 7, carrier frequency 3 is set; carrier frequency selection when MC_A11 and MC_B11 are selected. The same configuration can be used for carrier frequency selection when each MC is selected. FIG. 30 shows the carrier frequency setting in Example 8.

[0210] In Fig. 30, 197 is a selector that selects the carrier frequency (carrier frequency selected by the circuit in Fig. 29) when MC_A11 and MC_B11 switching commands are 1. 198 is a selector that selects the carrier frequency (carrier frequency selected by the same circuit as in Fig. 29) when MC_A21 and MC_B21 switching commands are 1. 199 is a selector that selects the carrier frequency (carrier frequency selected by the same circuit as in Fig. 29) when MC_A31 and MC_B31 switching commands are 1.

[0211] In Figure 30, when the MC_A11 and MC_B11 opening and closing commands are 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 commands are 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 commands are 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 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, half the rated current, and one-third the rated current. If the rated current when MC_A11 and MC_B11 are selected is smaller than half 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 referred to as carrier frequency 2. If the rated current when MC_A11 and MC_B11 are selected is smaller than half 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 referred to as carrier frequency 3. The carrier frequency is increased depending on the rated current value when MC_A11 and MC_B11 are selected.

[0214] The carrier frequency of the device must be appropriately set 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 opening and closing selection of each MC. The MC for connecting to the load opens and closes upon receiving a command after the opening and closing state of each MC has been determined. Therefore, if the carrier frequency is set according to the opening and closing command of each MC, the carrier frequency can be changed 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 opening or closing.

[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 sudden changes in current or increasing the carrier frequency.

[0216] REFERENCE SIGNS LIST 1, 2, 3... Power conversion device 200... Load HCT_A11, HCT_A21, HCT_A31... Current detector MC_A11, MC_A21, MC_A31, MC_C11... Electromagnetic contactor L_A11, L_A12, L_B11, L_B12, L_A21... Reactor 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 product circuit 30, 70, 130, 150... Current range switching processing unit 40, 140, 158... Current controller 53, 55, 72, 87, 91, 101, 118, 134, 154... Adder 56, 57, 92, 93, 96, 102... Comparators 60, 113 to 115, 124... OR circuits 61, 119... Opening and closing command / current control permission signal generating unit 120... Output side electromagnetic contactor opening and closing command generating unit 155... Output filter front side selector 156... Output filter rear side selector

Claims

1. A main circuit of the power conversion device is configured by providing a plurality of power conversion devices in parallel with a load, the main circuit being provided with 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 circuit connecting each of the power conversion devices and the load and are connected in series from the power conversion device to the load, and 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 a first electromagnetic contactor opening / closing command signal and a second electromagnetic contactor opening / closing command signal generated by the opening / closing command / current control permission signal generation unit are input, and a logical AND circuit which takes the 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 the output of the logical AND circuit; and a current controller which, when the current control permission signal generated by the opening / closing command / current control permission signal generation unit is control permission, performs 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, thereby generating a voltage command for the power conversion device, and when the current control permission signal is control prohibition, switches the current command, the proportional gain, and the integral gain to zero.

2. The main circuit of the power conversion device is configured by connecting in parallel between both ends of the first electromagnetic contactor a series circuit consisting of the second current detector, the second reactor, and the second electromagnetic contactor in a number equal to the number of installed power conversion devices, and the second electromagnetic contactor side AND circuit of the load connection permission determination processing unit has AND circuits for taking the logical product of the open / close setting signal of the second electromagnetic contactor and the operation permission signal when the second electromagnetic contactor is closed in a number 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 power conversion device according to claim 1, characterized in that the second electromagnetic contactor opening and closing command generating AND circuit of the opening and closing command / current control permission signal generating unit has AND circuits that take the logical product of a load connection permission signal and an opening and closing setting signal of the second electromagnetic contactor, the number of times corresponding to the number of installed power conversion devices, and the current control permission signal generating OR circuit is composed of an OR circuit that performs logical OR processing of an output of the first electromagnetic contactor opening and closing command generating AND circuit and each output of the second electromagnetic contactor opening and closing command generating AND circuit, the number of times corresponding to the number of installed power conversion devices, and 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 and closing command of the first electromagnetic contactor and the opening and 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 number of second electromagnetic contactors, the number of installed power conversion devices, depending on the addition result of the adder.

3. A main circuit of the power conversion device is provided with a plurality of power conversion devices in parallel with a load, the main circuit of the power conversion device being provided with 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, which are respectively inserted in an electric circuit connecting each of the power conversion devices and the load and are connected in series from the power conversion device 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, which are respectively 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 the negative terminal of the power conversion device; 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, the operation permission setting for the second electromagnetic contactor during output filter capacitor voltage control, and the operation permission setting for the third electromagnetic contactor during output filter capacitor voltage control that are each permitted; 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 that takes a logical AND of the opening / closing setting signal of the first electromagnetic contactor and the load connection permission signal; a second AND circuit that takes a logical AND of the opening / closing setting signal of the second electromagnetic contactor and the load connection permission signal; a third AND circuit that takes a logical AND of the opening / closing setting signal of the third electromagnetic contactor and the 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 the operation permission signal of the first electromagnetic contactor during output filter capacitor voltage control; a fifth AND circuit which takes a logical AND of a signal obtained by logically inverting the load connection permission signal, the output signal of the fourth comparator, and an operation permission signal at the second electromagnetic contactor during output filter capacitor voltage control; a sixth AND circuit which takes a logical AND of a signal obtained by logically inverting the load connection permission signal, the output signal of the fourth comparator, and an operation permission signal at the third electromagnetic contactor during output filter capacitor voltage control; a first OR circuit which performs a logical OR process on outputs of the first AND circuit and the fourth AND circuit to output an opening and closing command for the first electromagnetic contactor; a second OR circuit which performs a logical OR process on outputs of the second AND circuit and the fifth AND circuit to output an opening and closing command for the second electromagnetic contactor; and a third OR circuit which performs a logical OR process on outputs of the third AND circuit and the sixth AND circuit to output an opening and 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 depending on the addition result; a first AND circuit that takes the logical product of the opening / closing command of the first electromagnetic contactor and the opening / closing state signal of the first electromagnetic contactor outputted from the first OR circuit; a second AND circuit that takes the logical product of the opening / closing command of the second electromagnetic contactor and the opening / closing state signal of the second electromagnetic contactor outputted from the second OR circuit; and a third AND circuit that takes the logical product of the opening / closing command of the third electromagnetic contactor and the opening / closing state signal of the third electromagnetic contactor outputted from the third OR circuit. an output side electromagnetic contactor opening / closing command generating section including a first selector which outputs 1 when the load connection permission signal indicates permission and 0 when the load connection permission signal indicates non-permission and a fourth AND circuit which takes a logical AND between an output signal of the first selector and a signal resulting from performing a logical OR process on the outputs of the first to third AND circuits and outputs an output side electromagnetic contactor opening / closing command; a second selector which outputs 0 or 1 in response to the opening / closing command for the first electromagnetic contactor, outputs 0 or 2 in response to the opening / closing command for the second electromagnetic contactor, and outputs 0 or 3 in response to the opening / closing command for the third electromagnetic contactor, and an adder which adds up the outputs of the second selector, and which selects a current detection value of one of the first to third current detectors in response to the 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 plurality of power conversion devices are provided in parallel with a load, and a first current detector on the front side of an output filter having a first current rating, a first reactor, a first electromagnetic contactor on the front side of the output filter for selecting the first current detector, a first electromagnetic contactor on the 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 the rear side of the output filter having a first current rating, a fourth reactor, and an output side electromagnetic contactor are respectively inserted in an electric circuit connecting each of the power conversion devices and the load and sequentially connected in series from the power conversion device to the load; 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 selecting the second current detector, each connected in parallel to the series circuit of the first reactor and the output filter front-side first electromagnetic contactor, 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 selecting 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 pole 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 the output of the first logical OR circuit is changed to output an opening / closing command for a first electromagnetic contactor on the front side of an output filter and a first electromagnetic contactor on the rear side of the output filter, the output of the second logical OR circuit is changed to output 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 the output of the third logical OR circuit is changed to output 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; and an output side electromagnetic contactor opening / closing command generating unit as described in 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 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 and the state signal of the first electromagnetic contactor is changed to a state signal 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,an output side electromagnetic contactor opening / closing command generating unit configured to change 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 to change a 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, and to change the opening / closing command for the third electromagnetic contactor to an opening / closing command 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, and to change the 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 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, and 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 an output filter in response to an output of the adder; and 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 a 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. A power conversion device as described in 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 the states of the output side electromagnetic contactors connected to the main circuits of all power conversion devices connected in parallel are all closed when a current control enable signal specifying current control is output from the opening / closing command / current control enable signal generation unit.

6. A power conversion device as described in claim 4 or 5, characterized in that an operation permission setting determination unit is provided according to the number of parallel operation units of the power conversion device, and is configured to select the operation permission setting with the electromagnetic contactor closed for use in the load connection permission judgment processing unit for the electromagnetic contactor with the smallest number of openings and closings, based on the 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, the 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 the number of openings and closings of each electromagnetic contactor is counted according to the number of parallel operation units that has been set.

7. A power conversion device as described in claim 4 or 5, characterized in that a circuit between any one of a plurality of power conversion devices and a 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, 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.

8. a first carrier frequency selection unit which compares a rated current of the power conversion device with a rated current when the front first electromagnetic contactor and the rear 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 first electromagnetic contactor and the rear 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 first electromagnetic contactor and the rear first electromagnetic contactor of the output filter are selected, and selects one of first to third carrier frequencies which are set higher in frequency in accordance with the 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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