Power conversion device

Abstract

To provide a parallel configuration in which a plurality of power conversion devices having a plurality of current detectors different in rating and being provided with filter capacitors on the output side are connected in parallel such that oscillation of a load voltage is restrained.SOLUTION: When a voltage control permission signal for designating voltage control is outputted from a switch command / current voltage control permission signal generation unit and any one of output-side electromagnetic contacts which are respectively connected to a plurality of power conversion devices is in an open state, a voltage selection unit 70 selects output voltage detection. When all of the output-side electromagnetic contacts are in a closed state, the voltage selection unit selects a voltage command. When the voltage control permission signal designates voltage control, proportional control and integration control using a proportional gain and an integration gain determined so as to set a voltage detection value in an output filter capacitor equal to the voltage of the voltage command selected by the voltage selection unit, are performed to generate a current command.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a voltage control method when power conversion devices having multiple current detectors (hereinafter sometimes referred to as HCTs) with different ratings to control current with high precision and having a capacitor at the output are connected in parallel. [Background technology]

[0002] There is a demand for power conversion devices with large capacity and multiple current ratings. For this reason, it is necessary to develop a parallel operation method for multiple power conversion devices with multiple current ratings. In addition, there are also applications that require not only current control but also voltage control to control the voltage of the load.

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

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

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

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

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

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

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

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

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

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

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

[0014] When controlling the voltage of a load in a control configuration such as that shown in Fig. 3, the following problems arise. Here, a case is shown in which the output MC of the power conversion device 1 is closed and then the MC of the power conversion device 2 is closed. The opening and closing operation of the MC varies from part to part. In a large-capacity MC, it may take tens to hundreds of ms from the input of an opening and closing signal until it actually starts operating.

[0015] Assuming that the output voltage command is operated on a ramp after the MC is closed in each power conversion device, the load voltage is likely to oscillate because the difference between the command and the feedback signal becomes large. Furthermore, if the frequency at the time of oscillation is not within the control band, the oscillation cannot be suppressed. Furthermore, if the phase lag is large, the feedback loop becomes positive and diverges. As a result, the load voltage is not established. Figure 4 shows an example of the waveform when the load voltage control diverges.

[0016] Also, Fig. 5 shows examples of current waveforms in the steady state of the output current and load current of each power conversion device when carrier synchronization is not implemented. In Fig. 5, the carrier ripple is shown as a triangular wave. Because carrier synchronization is not implemented between the devices, the carrier ripple may occur equally between the devices. In this case, the carrier ripple of each device is superimposed on the current flowing to the load. Because the carrier ripple of two units occurs in the load current, the carrier ripple is larger than when only one unit is operated.

[0017] The issues that arise when operating multiple units by simply combining the outputs of the conventional technology are summarized below. 1. The difference between the command and feedback signal becomes large, and the load voltage is prone to oscillation. In the worst case scenario, the load voltage control diverges and the intended voltage value cannot be controlled. 2. When multiple units are operated, the output ripple of the power conversion device increases for each unit in parallel. This increases the ripple component of the output current, leading to an increase in harmonics and unintended losses on the load side. In addition, as the current ripple increases, the voltage ripple also increases proportionally, leading to a deterioration in accuracy if there are requirements for the voltage ripple. If a small output current is acceptable, the output ripple can be suppressed by operating only one unit. 3. When the output is configured as an LCL and the load has a capacitance component such as a battery, there is a possibility that a resonance phenomenon will occur due to the LC circuit. If the resonance frequency is not within the control band, it cannot be controlled and may diverge.

[0018] The present invention is devised to solve the above-mentioned problems, and its object is to provide a power conversion device that can suppress load voltage oscillations and the generation of output current ripples in a multiple-unit parallel configuration in which power conversion devices having multiple current ratings and equipped with filter capacitors on the output side are connected in parallel. [Means for solving the problem]

[0019] In order to solve the above problem, the power conversion device according to claim 1 is A plurality of power conversion devices are 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 an output filter for selecting the first current detector, a first electromagnetic contactor on a rear side of an output filter for selecting the first current detector on the rear side of an output filter, a first current detector on a rear side of an output filter having a first current rating, a fourth reactor, and an output side electromagnetic contactor are respectively inserted in an electric path connecting each of the power conversion devices and the load and are connected in series from the power conversion devices to the load, and a series circuit is composed of a second current detector on a front side of an output filter having a second current rating smaller than the first current detector, a second reactor, and a second electromagnetic contactor on a front side of an output filter 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 on the front side of the output filter, and a series circuit including a third current detector on an output filter front side having a third current rating smaller than the first current detector, a third reactor, and a third electromagnetic contactor on an 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 filter front side and the first electromagnetic contactor on the output filter rear side and a negative pole end of the power conversion device; a series circuit including a second electromagnetic contactor on an output filter rear side having a second current rating smaller than the first current detector and a second electromagnetic contactor on an output filter rear side that selects the second current detector, the series circuits being connected in parallel between both ends of the first electromagnetic contactor on the output filter rear side, and a third current detector on an output filter rear side having a third current rating smaller than the second current detector and a third electromagnetic contactor on an output filter rear side that selects the third current detector; a first magnetic contactor side logical AND circuit which takes a logical AND of a preset open / close setting signal of the first magnetic contactor on the front side of the output filter and the first magnetic contactor on the rear side of the output filter and a setting signal for permitting operation in a closed state of the first magnetic contactor on the front side of the output filter and the first magnetic contactor on the rear side of the output filter; a second electromagnetic contactor side AND circuit which takes a logical AND of a preset open / close setting 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 a setting signal to permit operation in a closed state 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; a third magnetic contactor side logical AND circuit which takes a logical AND of a preset open / close setting signal of the third magnetic contactor on the front side of the output filter and the third magnetic contactor on the rear side of the output filter and a setting signal for permitting operation in a closed state of the third magnetic contactor on the front side of the output filter and the third magnetic contactor on the rear side of the output filter; an operation permission setting side adder that adds up the numbers where the logical product results of the first to third electromagnetic contactor side AND circuits are 1, an open / close setting side adder that adds up the numbers where the open / close setting signals of the first to third electromagnetic contactors are closed, a first comparator that outputs 1 only when the added output of the operation permission setting side adder is equal to 1, and a second comparator that outputs 1 only when the added output of the open / close setting side adder is equal to 1; a third comparator that outputs 1 when an absolute value of a difference between a voltage detection value obtained by detecting a voltage of the output filter capacitor and a voltage detection value obtained by detecting a voltage on the load side of the output side electromagnetic contactor is smaller than a set voltage judgment level; a load connection permission determination processing unit having a load connection permission signal generating AND circuit which takes a logical AND of the outputs of the first comparator to the third comparator and outputs a signal which permits load connection when a logical AND condition is satisfied; a second adder on the operation permission setting side which adds up the numbers of preset operation permission settings 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 output filter capacitor voltage control, 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 output filter capacitor voltage control, and 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, respectively, which are permitted; and a fourth comparator which 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 an open / close setting 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 and a load connection permission signal; a second AND circuit that takes a logical AND of an open / close setting signal of the output filter front-side second electromagnetic contactor and the output filter rear-side second electromagnetic contactor and a load connection permission signal; a third AND circuit that takes a logical AND of an open / close setting 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 and a load connection permission signal; a fourth AND circuit that takes a logical AND of a signal obtained by logically inverting the load connection permission signal, an output signal of the fourth comparator, and an operation permission signal at 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 during the 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, an output signal of the fourth comparator, and an operation permission signal at 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 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, an output signal of the fourth comparator, and an operation permission signal at 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 output filter capacitor voltage control; a first logical sum circuit that performs logical sum processing on the outputs of the first logical sum circuit and the fourth logical sum circuit 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; a second AND circuit that performs a logical OR operation on the outputs of the second AND circuit and the fifth AND circuit to output 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; a third AND circuit that performs a logical OR operation on the outputs of the third AND circuit and the sixth AND circuit 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; a first selection circuit that performs a logical sum operation on the outputs of the first, second, and third logical AND circuits, and outputs 0 when the result is 0, and outputs 1 when the result is 1; a second selection circuit that performs a logical sum operation on the outputs of the fourth, fifth, and sixth AND circuits, and outputs 0 when the result is 0, and outputs 1 when the result is 1; a switching command / current / voltage control permission signal generating unit having a current / voltage 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 disallowance, current control, or output filter capacitor voltage control, or a voltage control permission signal of either voltage control disallowance, voltage control, or output filter capacitor voltage control according to a result of the addition; a first AND circuit that takes a logical AND of an opening / closing command for the first electromagnetic contactor on the front side of the output filter and the first electromagnetic contactor on the rear side of the output filter outputted from the first OR circuit and an opening / closing state 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; a second AND circuit that takes a logical AND of an opening / closing command for the output filter front-side second electromagnetic contactor and the output filter rear-side second electromagnetic contactor output from the second OR circuit and an opening / closing state signal for the output filter front-side second electromagnetic contactor and the output filter rear-side second electromagnetic contactor; a third AND circuit which takes a logical AND of an open / close 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 outputted from the third OR circuit and an open / close state 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; an output side electromagnetic contactor opening / closing command generating unit having a first selector that outputs 1 when the load connection permission signal is permission and 0 when the load connection permission signal is not permission, and a fourth AND circuit that takes a logical AND between the output signal of the first selector and a signal resulting from 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 voltage selection unit which selects output voltage detection if any of the output side electromagnetic contactors connected to the plurality of power conversion devices is in an open state when a voltage control permission signal specifying voltage control is output from the opening / closing command / current, voltage control permission signal generation unit, and which selects a voltage command if all of the output side electromagnetic contactors are in a closed state; When the voltage control permission signal output from the switching command, current, and voltage control signal generating section specifies voltage control, proportional control and integral control are performed using the set proportional gain and integral gain so that the voltage detection value of the output filter capacitor becomes the voltage of the voltage command selected by the voltage selection section, and a current command is generated. When the voltage control permission signal specifies filter capacitor voltage control, a proportional control and an integral control are performed by the proportional gain and the integral gain so that a voltage detection value of an output filter capacitor becomes a detection value of an output voltage, thereby generating a current command; a voltage control unit including a voltage controller that switches a voltage command, a proportional gain, and an integral gain to zero when the voltage control permission signal specifies that voltage control is not permitted; a current range switching processing section including: a second selector that outputs 0 or 1 in response 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, outputs 0 or 2 in response 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 outputs 0 or 3 in response 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; an output filter front-side selector that has an adder that adds up outputs, and that selects one of the current detection values ​​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 one of the current detection values ​​of the first to third current detectors on the rear side of the output filter in response to an output of the adder; When the current control permission signal generated by the switching command / current, voltage control permission generating unit is a current control, a proportional control and an integral control are performed by a proportional gain and an 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; When the current control permission signal is output filter capacitor voltage control, a proportional control and an integral control are performed by a proportional gain and an integral gain so that the current detection value selected by the current range switching processing unit becomes a current command value during the set output filter capacitor voltage control, thereby generating a voltage command for the power conversion device; The motor drive device is characterized by comprising a current controller which switches a current command, a proportional gain and an integral gain to zero when the current control permission signal indicates that current control is not permitted. The power conversion device according to claim 2 is the power conversion device according to claim 1, The power converter is characterized by comprising a current control selector that enables a current control input of the current controller when all output side electromagnetic contactors provided in a plurality of power conversion devices are in a closed state, and a command selector that selects a current control output current command when current control is selected by a control selection signal, and a voltage control output current command when voltage control is selected, and sets the selected command as the current control input of the current controller. The power conversion device according to claim 3 is the power conversion device according to claim 1 or 2, a voltage selection unit which selects output voltage detection if any of the output side electromagnetic contactors connected to the plurality of power conversion devices is in an open state when a voltage control permission signal specifying voltage control is output from the opening / closing command / current, voltage control permission signal generation unit, and which selects a voltage command if all of the output side electromagnetic contactors are in a closed state; When the voltage control permission signal output from the switching command / current and voltage control signal generating unit specifies voltage control, proportional control is performed using a proportional gain set under the condition that all of the output side electromagnetic contactors are in the closed state, and integral control is performed using an integral gain so that the voltage detection value of the load voltage becomes the voltage of the voltage command selected by the voltage selecting unit, and a load voltage compensation command is output when all of the output side electromagnetic contactors are in the closed state; When the voltage control permission signal specifies filter capacitor voltage control, proportional control is performed using a proportional gain and integral control is performed using an integral gain, which are set under the condition that all of the output side electromagnetic contactors are in a closed state, so that the detected value of the load voltage becomes the output voltage detected value selected by the voltage selection unit, and a load voltage compensation command is output when all of the output side electromagnetic contactors are in a closed state; a load voltage compensation control unit having a voltage command and a load voltage compensator for switching a proportional gain and an integral gain to zero when the voltage control permission signal specifies that voltage control is not permitted; The voltage control unit is characterized by comprising a superimposing unit that superimposes a load voltage compensation command output from the load voltage compensator on a voltage command or an output voltage detection value input to a voltage controller of the voltage control unit. The power conversion device according to claims 4 and 5 is characterized in that, in claims 1, 2, and 3, The inverter circuit is characterized in that it comprises a reactor bypass electromagnetic contactor connected in parallel to the series assembly of the fourth reactor and the output side electromagnetic contactor, and an electromagnetic contactor opening and closing command generating unit that generates an opening and closing command to close the output side electromagnetic contactor and open the reactor bypass electromagnetic contactor, and an opening and closing command to open the output side electromagnetic contactor and close the reactor bypass electromagnetic contactor, based on the output side electromagnetic contactor opening and closing command output from a fourth AND circuit of the output side electromagnetic contactor opening and closing command generating unit. The power conversion device according to claims 6 and 7 is characterized in that, The device is characterized by having a control selection unit that selects an opening / closing command to close the output side electromagnetic contactor and open the reactor bypass electromagnetic contactor when performing current control, and selects an opening / closing command to open the output side electromagnetic contactor and close the reactor bypass electromagnetic contactor when performing voltage control. Effect of the Invention

[0020] (1) According to the invention described in claims 1 to 7, the voltage of each of the output filter capacitors connected to the output side of the parallel-connected power conversion devices can be controlled, eliminating voltage interference between the devices. This makes it possible to suppress the oscillation of the load voltage and the generation of output current ripples. (2) According to the invention as set forth in claim 3, the load voltage is detected and compensated for before voltage control is performed, so that the load voltage can be controlled with high accuracy. (3) According to the inventions described in claims 4 to 7, by bypassing the final stage reactor (fourth reactor) on the output side during voltage control, it is possible to eliminate the possibility of resonance of the current flowing through the load caused by the circuit impedance of the final stage reactor and the load. In addition, since there is no voltage drop in the output side reactor, more accurate voltage control is possible. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a configuration diagram showing an example of a power conversion device including multiple HCTs with different current ratings according to the prior art. [Diagram 2] FIG. 1 is a configuration diagram showing a case where outputs of power conversion devices according to the prior art are combined to operate a plurality of power conversion devices. [Diagram 3] FIG. 13 is a control configuration diagram when prior art is combined. [Figure 4] FIG. 4 is a waveform diagram showing a case where the load voltage control in the control of FIG. 3 diverges. [Diagram 5] FIG. 4 is a current waveform diagram of each part in the control of FIG. 3. [Figure 6] 1 is a main circuit configuration diagram of a power conversion device according to a first embodiment of the present invention. [Figure 7] FIG. 2 is a diagram showing an HCT selection MC opening and closing control configuration in the first embodiment of the present invention. [Figure 8] FIG. 2 is a diagram showing an output MC switching control configuration according to the first embodiment of the present invention. [Figure 9] 1 is an overall configuration diagram of voltage control in the first embodiment of the present invention. [Figure 10] FIG. 2 is a voltage control configuration diagram according to the first embodiment of the present invention. [Figure 11] FIG. 2 is a current control configuration diagram of the power conversion device according to the first embodiment of the present invention. [Figure 12] FIG. 11 is an overall configuration diagram of voltage control according to a second embodiment of the present invention. [Figure 13] 13 is a configuration diagram of a load voltage compensation control according to a second embodiment of the present invention. [Figure 14] FIG. 11 is a voltage control configuration diagram according to a second embodiment of the present invention. [Figure 15] 11 is a main circuit configuration diagram of a power conversion device according to a third embodiment of the present invention. [Figure 16] FIG. 11 is a diagram showing an output MC switching control configuration according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiment. As a prerequisite for the present invention, the following circuit configuration will be described.

[0023] 1. Carrier synchronization is not performed between paralleled power conversion devices. 2. The power conversion device is not limited to one having a flying capacitor. EXAMPLES

[0024] FIG. 6 shows a main circuit configuration of the power conversion device in the first embodiment.

[0025] In FIG. 6, a plurality of power conversion devices 1, 2 are provided in parallel with respect to a load 200, and in an electric circuit connecting the power conversion device 1 and the load 200, the following are connected in series from the power conversion device 1 to the load 200: a first current detector HCT_A11 on the front side of the output filter having a first current rating, a first reactor L_A11 having a first inductance value, a first electromagnetic contactor MC_A11 on the front side of the output filter that selects the first current detector HCT_A11, a first electromagnetic contactor MC_B11 on the rear side of the output filter that selects the first current detector HCT_B11 on the rear side of the output filter, a first current detector HCT_B11 on the rear side of the output filter, a fourth reactor L_B11, and an output side electromagnetic contactor MC_C11. Between the common connection point of HCT_A11 and the first reactor L_A11 and the common connection point of MC_A11 and MC_B11, there are connected in parallel 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 HCT_A11, a second reactor L_A21 having a second inductance value, and a second electromagnetic contactor MC_A21 on the front side of the output filter that selects HCT_A21, 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 HCT_A21, a third reactor L_A31 having a third inductance value, and a third electromagnetic contactor MC_A31 on the front side of the output filter that selects HCT_A31. An output filter capacitor C11 is connected between the common connection point of MC_A11 and MC_B11 and the negative electrode side of the power conversion device 1. Connected in parallel between both ends of the MC_B11 are a series circuit of a second current detector HCT_B21 on the rear side of the output filter having a second current rating smaller than that of HCT_B11 and a second electromagnetic contactor MC_B21 on the rear side of the output filter which selects HCT_B21, and a series circuit of a third current detector HCT_B31 on the rear side of the output filter having a third current rating smaller than that of HCT_B21 and a third electromagnetic contactor MC_B31 on the rear side of the output filter which selects HCT_B31. The main circuit of the electric path connecting the power conversion device 2 and the load 200 is configured in the same manner as above, with the suffixes at the end of HCT_A, HCT_B, LA, LB, MC_A, MC_B, and MC_C changed from "1" to "2." In addition, C12 is connected as the output filter capacitor. By applying the configuration of this example, 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 diagram has the following features: (1) There are HCTs before and after the output filter. The one before the filter is HCT_A and the one after the filter is HCT_B. (2) The combinations of current ratings, HCT, and MC are defined as shown in Table 1.

[0026] [Table 1]

[0027] Table 1 shows only one unit, but other power conversion devices are defined in the same way. The main circuit configuration of this embodiment is intended to have a capacitor at the output. In this example, the output filter is in the form of an LCL. In addition, a switch (output side electromagnetic contactors MC_C11, MC_C12) for disconnecting the load is provided after the L in the final stage of the LCL.

[0028] Fig. 7 shows a configuration diagram of the HCT selection MC switching control in the embodiment 1. In Fig. 7, reference numeral 10 denotes a load connection permission determination processing unit that determines whether to permit or not permit a load connection, and is configured as follows.

[0029] Reference numeral 11 denotes a logical AND circuit which takes the logical AND of a preset open / close setting signal for the output filter front side electromagnetic contactor MC_A11 and the output filter rear side electromagnetic contactor MC_B11 and an operation permission setting signal with MC_A11 and MC_B11 closed.

[0030] Reference numeral 12 denotes a logical AND circuit which takes the logical AND of a preset open / close setting signal for the output filter front side electromagnetic contactor MC_A21 and the output filter rear side electromagnetic contactor MC_B21 and an operation permission setting signal with MC_A21 and MC_B21 closed.

[0031] Reference numeral 13 denotes a logical AND circuit which takes the logical AND of a preset open / close setting signal for the output filter front side electromagnetic contactor MC_A31 and the output filter rear side electromagnetic contactor MC_B31 and an operation permission setting signal with MC_A31 and MC_B31 closed. Reference numerals 14 to 16 denote selectors which select 0 when the output of each of the AND circuits 11 to 13 is 0 and select 1 when the output is 1, and reference numeral 21 denotes an operation permission setting side adder which adds a number which is 1 as the selection result of the selectors 14 to 16. Numerals 17 to 19 are selectors which select 0 when the opening and closing setting signals of MC_A11 and MC_B11, the opening and closing setting signals of MC_A21 and MC_B21, and the opening and closing setting signals of MC_A31 and MC_B31 are 0, and select 1 when the opening and closing setting signals are 1, and 22 is an opening and closing setting side adder which adds the number when the selection result of selectors 17 to 19 is 1.

[0032] Reference numeral 23 denotes a comparator which outputs 1 only when the sum output of the operation permission setting side adder 21 is equal to 1; 24 denotes a comparator which outputs 1 only when the sum output of the open / close setting side adder 22 is equal to 1.

[0033] Reference numeral 25 denotes a subtractor that takes the difference between the voltage detection value of the output filter capacitor C11 and the secondary side voltage detection value of the output side electromagnetic contactor MC_C11, and reference numeral 26 denotes an absolute value processor that takes the absolute value of the difference output of the subtractor 25.

[0034] Reference numeral 27 denotes a comparator which outputs 1 when the absolute value of the absolute value processor 26 is smaller than a set voltage judgment level.

[0035] Reference numeral 28 denotes a logical AND circuit for generating a load connection permission signal that takes the logical AND of the outputs of the comparators 23, 24, and 27, and outputs a load connection permission signal that specifies permission 1 when the logical AND condition is satisfied and specifies non-permission 0 when the logical AND condition is not satisfied. 31 is a selector which selects 0 when the operation permission setting signal in 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 during filter capacitor voltage control is not permitted, and selects 1 when the operation permission setting signal is permitted. 32 is a selector which selects 0 when the operation permission setting signal in the output filter front-side second electromagnetic contactor MC_A21 and the output filter rear-side second electromagnetic contactor MC_B21 during filter capacitor voltage control is not permitted, and selects 1 when the operation permission setting signal is permitted. Reference numeral 33 denotes a selector which selects 0 when the operation permission setting signal in 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 during filter capacitor voltage control is not permitted, and selects 1 when the operation permission setting signal is permitted. Reference numeral 34 denotes a second adder on the operation permission setting side that adds up the number when the selection result of each of the selectors 31 to 33 is 1, and 35 denotes a comparator that outputs 1 only when the addition output of the adder 34 is equal to 1. Reference numeral 36 denotes a logical AND circuit which takes the logical AND of the load connection permission signal output from the logical AND circuit 28 and the opening and closing setting signals of MC_A11 and MC_B11, reference numeral 37 denotes a logical AND circuit which takes the logical AND of the load connection permission signal output from the logical AND circuit 28 and the opening and closing setting signals of MC_A21 and MC_B21, and reference numeral 38 denotes a logical AND circuit which takes the logical AND of the load connection permission signal output from the logical AND circuit 28 and the opening and closing setting signals of MC_A31 and MC_B31.

[0036] Reference numerals 39 to 41 denote NOT circuits which logically invert the load connection permission signals.

[0037] Reference numeral 50 denotes a logical AND circuit which takes the logical AND of the output of the NOT circuit 39, the output of the comparator 35, and the operation permission setting signals in MC_A11 and MC_B11 during the filter capacitor voltage control.

[0038] Reference numeral 51 denotes a logical AND circuit which takes the logical AND of the output of the NOT circuit 40, the output of the comparator 35, and the operation permission setting signals in MC_A 21 and MC_B 21 during the filter capacitor voltage control.

[0039] Reference numeral 52 denotes a logical AND circuit which takes the logical AND of the output of the NOT circuit 41, the output of the comparator 35, and the operation permission setting signals in MC_A31 and MC_B31 during the filter capacitor voltage control.

[0040] Reference numeral 53 denotes a logical sum circuit that performs logical sum processing on the outputs of the logical sum circuit 36 ​​and the logical sum circuit 50 and outputs an opening / closing command for the output filter front-side first electromagnetic contactor MC_A11 and the output filter rear-side first electromagnetic contactor MC_B11.

[0041] Reference numeral 54 denotes a logical OR circuit that performs logical OR processing on the outputs of the logical AND circuit 37 and the logical AND circuit 51 and outputs an opening / closing command for the output filter front-side second electromagnetic contactor MC_A21 and the output filter rear-side second electromagnetic contactor MC_B21.

[0042] Reference numeral 55 denotes a logical OR circuit that performs logical OR processing on the outputs of the logical AND circuit 38 and the logical AND circuit 52 and outputs an opening / closing command for the output filter front-side third electromagnetic contactor MC_321 and the output filter rear-side third electromagnetic contactor MC_B31.

[0043] Reference numeral 56 denotes a first selection circuit which performs a logical sum operation on the outputs of the logical product circuits 36 to 38, and outputs 0 when the result is 0, and 1 when the result is 1.

[0044] Reference numeral 57 denotes a second selection circuit which performs a logical sum operation on the outputs of the logical product circuits 50 to 52, and outputs 0 when the result is 0, and 2 when the result is 1.

[0045] Reference numeral 58 denotes a current / voltage control permission signal generating adder that adds the outputs of the first selection circuit 56 and the second selection circuit 57 and outputs, depending on the addition result, a current control permission signal which is either current control disallowance, current control, or output filter capacitor voltage control, or a voltage control permission signal which is either voltage control disallowance, voltage control, or output filter capacitor voltage control. Incidentally, the circuit from the selectors 31 to 33 to the adder 58 constitutes an opening and closing command / current, voltage control permission signal generating unit 59. Although FIG. 7 shows a configuration diagram of the power conversion device 1, the power conversion device 2 may also have a similar configuration. In Fig. 7, the logical product of the open / closed setting of each MC and the closed operation permission setting is taken by logical product circuits 11 to 13. If the result of the logical product is 0, 0 is output, and if it is 1, 1 is output. The outputs for all MCs are added (adder 21) and the result is compared with 1, and if they are equal, 1 is output, and if they are not equal, 0 is output (comparator 23). When the MC open / close setting is 0, 0 is output, and when it is 1, 1 is output. The results for all MCs are added by an adder 22 and the result is compared with 1. If they are equal, 1 is output; if they are not equal, 0 is output (comparator 24). The difference between the output filter capacitor voltage detection value and the MC_C11 secondary side voltage detection value is subjected to absolute value processing (subtractor 25, absolute value processor 26). If the processed result is smaller than the voltage judgment level, it is set to 1, and if it is larger, it is set to 0 (comparator 27). The logical product of the results of the comparators 23, 24, and 27 is taken by the logical product circuit 28 to produce a load connection permission signal. The logical products of the load connection permission signal and the MC switching settings are taken by logical product circuits 36 to 38 to produce each MC switching command. The logical sum of these MC switching commands is used to generate a current control permission signal. During voltage control to make the output filter capacitor equal to the load voltage, if the MC operation permission setting is 0, it is set to 0; if it is 1, it is set to 1; the outputs of the operation permission settings of each MC are added (adder 34) and if the setting is 1, it is set to 1; otherwise, it is set to 0 (comparator 35). The logical product of the MC operation permission setting during output filter capacitor voltage control, the output signal of the comparator 35, and the logically inverted load connection permission signal is calculated by logical product circuits 50 to 52. A logical sum is taken from the results of the AND circuits 50 to 52, and if the result is 0, it is set to 0, and if the result is 1, it is set to 2 (second selection circuit 57). A logical sum is taken for the opening and closing commands of each MC (outputs of AND circuits 36 to 38), and if the result is 0, it is set to 0, and if the result is 1, it is set to 1 (first selection circuit 56). The results of the selection circuits 56 and 57 are added (by the adder 58) to produce a current control permission signal and a voltage control permission signal. The configuration of the output side electromagnetic contactor opening / closing control is shown in Fig. 8. In Fig. 8, the output side electromagnetic contactor opening / closing command generating unit 60 is configured as follows. 7, the logical product of the opening and closing commands of MC_A11 and MC_B11 and the status signals of MC_A11 and MC_B11 is obtained by a logical product circuit 61. The logical product of the opening and closing commands of MC_A21 and MC_B21 and the status signals of MC_A21 and MC_B21 is obtained by a logical product circuit 62. The logical product of the opening and closing commands of MC_A31 and MC_B31 and the status signals of MC_A31 and MC_B31 is obtained by a logical product circuit 63.

[0046] The logical sum of the logical product results of the logical product circuits 61 to 63 is taken by a logical sum circuit 64. When the load connection permission signal described in Fig. 7 is "disallowed 0", an MC_C11 open command 0 is selected by a selector 65, and when the load connection permission signal is "allowed 1", an MC_C11 close command 1 is selected by a selector 65.

[0047] A logical AND circuit 66 takes the logical AND of the outputs of the logical OR circuit 64 and the selector 65, and outputs an opening / closing command for MC_C11.

[0048] The overall configuration of voltage control is shown in Figure 9. The voltage control command is input, and voltage control is performed by applying the capacitor voltage of the output filter to the feedback signal. The output of the voltage control is set as a current command. Current control is performed using the current command and the current detection signal to generate a voltage command.

[0049] The configuration of the voltage control unit is shown in Fig. 10. In Fig. 10, 70 is a voltage selection unit that takes the logical product of the status signal (0,1) of MC_C11 on the power conversion device 1 side and the status signal (0,1) of MC_C12 on the power conversion device 2 side in a logical product circuit 71, selects output voltage detection when any of the output side electromagnetic contactors is in an open state (0), and selects a voltage command when all of the output side electromagnetic contactors are in a closed state (1). Reference numeral 72 denotes a selector which selects 0 when the voltage control permission signal indicates voltage control not permitted (0), selects 1 (the output of the voltage selection unit 70) when the voltage control permission signal indicates voltage control (1), and selects the output voltage detection value (2) when the filter capacitor voltage control signal indicates filter capacitor voltage control (2). Reference numeral 73 denotes a voltage controller that generates a current command by performing proportional control and integral control using a set proportional gain Kp and integral gain Ki so that the voltage detection value of the output filter capacitor becomes the voltage of the voltage command selected by the voltage selection unit 70 when the voltage control permission signal specifies voltage control. In FIG. 10, the inputs to the voltage controller 73 are as follows: If the voltage control permission signal is 0, set it to 0. When the voltage control permission signal is 1 and the output MC of all devices connected in parallel are open, output voltage detection is performed. When the voltage control permission signal is 1 and all output MCs of devices connected in parallel are closed, a voltage command is issued. When the voltage control permission signal is 2, output voltage detection is performed. (2) The feedback signal for voltage control is the detected capacitor voltage value of the output filter. (3) The proportional gain of voltage control is as follows. When the voltage control permission signal is 0, the proportional gain is 0. When the voltage control permission signal is 1 or 2, the proportional gain is Kp. (4) The integral action of voltage control is as follows. When the voltage control permission signal is 0, the initial value of the integral term is set. When the voltage control permission signal is 1 or 2, the previous value is set by the delay device 74 and integral action is performed. 75 is a limiter provided on the integral term side. The overall control operation mainly involves voltage control to control the capacitor voltage of the output filter. This allows control of the output filter capacitors of each power conversion device connected in parallel, eliminating interference between voltage controls of each device. The operation of voltage control is explained below. When the voltage control permission signal is 0, the input is 0 and the proportional gain is 0, so the function is turned off. When the voltage control permission signal is 2, it operates so that the output voltage detection value and the detected voltage of the filter capacitor match. When the voltage control permission signal is 1, when the output MC is open, it operates so that the output voltage detection value and the detected voltage of the filter capacitor match. When the output MC is closed, it operates so that the voltage command and the voltage of the filter capacitor match. A current control configuration diagram is shown in Fig. 11. In Fig. 11, 80 is a current range switching processing unit, which is configured as follows: 81 is a selector that outputs 0 or 1 in response to opening and closing commands 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, outputs 0 or 2 in response to opening and closing commands for MC_A21 and MC_B21, and outputs 0 or 3 in response to opening and closing commands for MC_A31 and MC_B31.

[0050] Reference numeral 82 denotes an adder that adds the output of the selector 81. Reference numeral 83 denotes an output filter front-side selector that selects each current detection value of the output filter front-side current detectors HCT_A11, HCT_A21, and HCT_A31 in response to the output of the adder 82. Reference numeral 84 denotes an output filter rear side selector which selects each current detection value of the output filter rear side current detectors HCT_B11, HCT_B21, and HCT_B31 in response to the output of the adder 82. The selected output (current detection value) of the output filter front side selector 83 is used as a feedback signal on the proportional control side of a current controller 88 . The output (current detection value) side of the output filter rear-side selector 84 is connected to a 1-side terminal of a selector 85 that switches the current detection value according to the current control permission signal of 0, 1, or 2. The 0-side terminal and the 2-side terminal of the selector 85 are connected to the output terminal of the output filter front-side selector 83. The selected output (current detection value) of the selector 85 is used as a feedback signal for the integral control side of the current controller 88 . Reference numeral 86 denotes a command selector which selects a current-controlled current command (0) when the set control selection signal is current control (0), and which selects a voltage-controlled output current command when the set control selection signal is voltage control (1). A current control selector 87 selects 0 when the output of the AND circuit 71 is 0, and selects the current command selected by the command selector 86 when the output is 1. Reference numeral 72 denotes a selector which selects 0 when the current permission signal is 0, selects the output of a current control selector 87 when the current permission signal is 1, and selects the current command value during filter capacitor voltage control when the current permission signal is 2. The output of selector 72 becomes the input of a current controller 88. When the current control permission signal indicates current control, the current controller 88 performs proportional control and integral control using a proportional gain Kp and an integral gain Ki so that the current detection value selected by the selectors 83, 84, and 85 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 current control is not permitted, the current command, the proportional gain, and the integral gain are switched to zero. In the integral operation, when the current control permission signal is 0, an initial integral value is set, and when it is 1 or 2, the previous value is set by the delay unit 89 and the integral operation is performed. The current control in FIG. 11 will be described. Since proportional control is the dominant control for speeding up the response, 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. Since integral control is the dominant control for eliminating steady-state error, the current detection value detected by the HCT after the filter, which removes high-frequency components and can detect low-frequency regions with high accuracy, is set as the feedback signal. This enables highly responsive and accurate current control to be achieved. 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, because it is necessary to control the current value flowing into the filter capacitor. As described above, according to the first embodiment, the voltages of the output filter capacitors connected to the output sides of the parallel-connected power conversion devices can be controlled individually, eliminating voltage interference between the devices. This makes it possible to suppress the oscillation of the load voltage and the generation of output current ripples. EXAMPLES

[0051] Figure 12 shows the overall configuration of voltage control in the second embodiment. Load voltage compensation is performed with a voltage control command as input. The output of the load voltage compensation, the voltage control command, and the capacitor voltage detection of the output filter are input to the voltage control. The output of the voltage control is set as a current command. The HCT selection MC switching control configuration in the second embodiment is configured in the same manner as that shown in FIG. 7 of the first embodiment, the output MC switching control configuration in the second embodiment is configured in the same manner as that shown in FIG. 8, and the current control configuration of the power conversion device in the second embodiment is configured in the same manner as that shown in FIG. 11. A configuration diagram of the load voltage compensation control in the second embodiment is shown in Fig. 13. In Fig. 13, reference numeral 101 denotes a logical AND circuit of the state signals (0: open, 1: closed) of the output side electromagnetic contacts MC_C11 and MC_C12 of the power conversion devices connected in parallel. A selector 102 selects output voltage detection (0) when the output of the AND circuit 101 is 0 (MC open) and selects a voltage command (1) when the output is 1 (all MCs closed). Reference numeral 103 denotes a selector which selects 0 when the voltage control permission signal output from the current / voltage control permission signal generating adder 58 in FIG. 7 indicates that voltage control is not permitted (0), selects the selected output of the selector 102 in the case of voltage control (1), and selects output voltage detection in the case of filter capacitor voltage control (2). The selected output of selector 103 is deviated from the load voltage detection value and becomes the input to load voltage compensator 104. When the voltage control permission signal specifies voltage control, load voltage compensator 104 performs proportional control using a proportional gain set on the condition that all output side electromagnetic contactors are in the closed state and integral control using an integral gain so that the load voltage detection value becomes the voltage of the voltage command selected by selectors 102 and 103, and outputs a load voltage compensation command when all output side electromagnetic contactors are in the closed state. In addition, when the voltage control permission signal specifies filter capacitor voltage control, proportional control is performed using a proportional gain set on the condition that all output side electromagnetic contactors are in the closed state, and integral control is performed using an integral gain so that the load voltage detection value becomes the output voltage detection value selected by the selectors 102, 103, and a load voltage compensation command is output when all output side electromagnetic contactors are in the closed state. Furthermore, when the voltage control permission signal specifies that voltage control is not permitted, the voltage command, the proportional gain, and the integral gain are switched to zero. In the load voltage compensator 104, when the voltage control permission signal is 0, an initial value of the integral term is set, and when it is 1 or 2, the previous value is set by a delay device 105 and integral operation is performed. Reference numeral 106 denotes a limiter provided on the integral term side. (1) The input to the load voltage compensation 104 is as follows: If the voltage control permission signal is 0, set it to 0. When the voltage control permission signal is 1 and the output MC of all devices connected in parallel are open, output voltage detection is performed. When the voltage control permission signal is 1 and all output MCs of devices connected in parallel are closed, a voltage command is issued. When the voltage control permission signal is 2, output voltage detection is performed. (2) The feedback signal of the load voltage compensator is the detected load voltage value. (3) The proportional gain of the load voltage compensation is as follows. When the voltage control permission signal is 0, the proportional gain is 0. When the voltage control permission signal is 1 or 2, the proportional gain is Kp. (4) The integral action of the load voltage compensator 104 is as follows: When all outputs MC of devices connected in parallel are open, the integral term is set to 0. When all the output MCs of the parallel-connected devices are closed, it is determined by the voltage control permission signal. When the voltage control permission signal is 0, the integral term initial value is set. When the voltage control permission signal is 1 or 2, the previous value is set and integral action is performed. (5) The output of the load voltage compensation 104 is: When all the outputs MC of the devices connected in parallel are open, the value is set to 0. When all output MCs of devices connected in parallel are closed, set the output of the load voltage control. A voltage control configuration diagram in the second embodiment is shown in Fig. 14. In Fig. 14, the same parts as in Fig. 10 are denoted by the same reference numerals. Fig. 14 differs from Fig. 10 in that a superimposition unit is provided that superimposes the load voltage compensation command generated by the load voltage compensator 104 in Fig. 13 on the voltage command or output voltage detection value (output of selector 72) input to voltage controller 73, and other parts are configured in the same way as in Fig. 10. In the overall operation of the voltage control in Figures 13 and 14, the main voltage control is to control the capacitor voltage of the output filter. This allows the output filter capacitors of each power conversion device connected in parallel to be controlled, eliminating interference in voltage control between each device. With this alone, there is a possibility that the voltage cannot be controlled to the intended level due to voltage drops caused by reactors, MCs, and wiring between the output filter capacitor and the load. For this reason, load voltage compensation control is implemented to feed back the load voltage, and the output is added to the voltage command and used as the input for voltage control. The time constant of the load voltage compensation control should be set to be about 10 times slower than that of the voltage control. This eliminates interference with voltage control. The operation of the load voltage compensation control is explained below. When the voltage control permission signal is 0, the input is 0 and the proportional gain is 0, so the function is turned off. When the voltage control permission signal is 2, the output MC is not closed basically, so the output of the load voltage compensation is 0 and the function is turned off. When the voltage control permission signal is 1, the function is enabled. If the load voltage compensation is enabled when the output MC is open, the power conversion device and the load are disconnected, so the load voltage cannot be controlled. If the integral term becomes enabled in this state, it will diverge due to the integral action. To prevent this, an action is added to set the integral term to 0 when the output MC is open. When the output MC is closed, the load voltage compensation control works so that the voltage command and the load voltage are equal. The operation of voltage control is explained below. When the voltage control permission signal is 0, the input is 0 and the proportional gain is 0, so the function is turned off. When the voltage control permission signal is 2, it operates so that the output voltage and the filter capacitor voltage match. The case when the voltage control permission signal is 1 is explained below. When the output MC is open, it operates so that the output voltage and the filter capacitor voltage match. When the output MC is closed, it operates so that the voltage command plus the load voltage compensation command matches the filter capacitor voltage. With this operation, the voltage command, which takes into account the voltage drop due to the reactor, MC, and wiring, matches the filter capacitor voltage, and as a result, the voltage command matches the load voltage. As described above, according to the second embodiment, the load voltage is detected, the load voltage is compensated, and then the voltage is controlled, so that the load voltage can be controlled with high accuracy. EXAMPLES

[0052] Fig. 15 shows a main circuit configuration diagram of a power conversion device in Example 3. In Fig. 15, the same parts as in Fig. 6 are denoted by the same reference numerals. Fig. 15 differs from Fig. 6 in that a reactor bypass electromagnetic contactor MC_C21 is connected in parallel to the series body of the fourth reactor L_B11 and the output side electromagnetic contactor MC_C11, and a reactor bypass electromagnetic contactor MC_C22 is connected in parallel to the series body of the fourth reactor L_B12 and the output side electromagnetic contactor MC_C12. Other parts are configured in the same way as in Fig. 6. Figure 16 shows an output MC switching control configuration diagram in Example 3. In Figure 16, the same parts as in Figure 8 are denoted by the same reference numerals. In Figure 16, a switching selection unit 110 is provided on the output side of the AND circuit 66 of the electromagnetic contactor switching command generation unit 60 described in Figure 8, which generates a switching command to close the output side electromagnetic contactor MC_C11 and open the reactor bypass electromagnetic contactor MC_C21, and a switching command to open the MC_C11 and close the MC_C11. The open / close selection unit 110 includes a selector 111 which selects 0 (output of AND circuit 66) when the control selection signal is 0 (current command) and 1 (open command) when the control selection signal is 1 (voltage control), and a selector 112 which selects 0 (open command) when the control selection signal is 0 (current command) and 1 (output of AND circuit 66) when the control selection signal is 1 (voltage control). The selection output of the selector 111 is an MC_C11 opening / closing command, and the selection output of the selector 112 is an MC_C21 opening / closing command. In Figure 15, during current control, MC_C11 is closed and MC_C21 is open. The output filter is in the form of an LCL that removes current harmonics. During voltage control, MC_C11 is open and MC_C21 is closed. If load 200 is a capacitor, resonance may occur due to the inductance of the final stage and the capacitance of the load. If a route does not pass through the final stage reactor during voltage control, resonance can be prevented. In the MC switching control of Fig. 16, a signal is prepared that is set as the control selection signal to 0 during current control and 1 during voltage control. When the control selection signal is 0, MC_C11 operates in the same manner as in the MC switching operation of the first embodiment, and MC_C21 remains at the open command. When the control selection signal is 1, MC_C11 remains at the open command, and MC_C21 operates in the same manner as in the MC switching operation of the first embodiment. In this way, it becomes possible to appropriately set the switching commands of the output MCs MC_C11 and MC_C21 during current control and voltage control. A similar output MC switching control configuration diagram can be used for devices connected in parallel. As described above, according to the third embodiment, by bypassing the final stage reactor (fourth reactor) on the output side during voltage control, it is possible to eliminate the possibility of resonance of the current flowing through the load caused by the circuit impedance of the final stage reactor and the load. In addition, since there is no voltage drop in the output side reactor, more accurate voltage control is possible. [Explanation of symbols]

[0053] 1, 2...Power conversion device 200…load HCT_A11, HCT_A21, HCT_A31…Current detectors MC_A11, MC_A21, MC_A31, MC_C11...Magnetic contactor L_A11, L_A12, L_B11, L_B12, L_A21...Reactors 10...Load connection permission determination processing unit 11~13, 28, 36~38, 50~52, 61~63...Logical AND circuit 21, 22, 34, 58, 82…Adder 23, 24, 27...Comparators 53~55, 64...OR circuit 59...Opening and closing command, current, voltage control permission signal generator 60…Magnetic contactor opening / closing command generation unit 73...Voltage regulator 83...Output filter front selector 84...Output filter rear selector 86...Command selector 88...Current controller 104...Load voltage compensator 110…Open / close selection section

Claims

1. A plurality of power conversion devices are 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 an output filter for selecting the first current detector, a first electromagnetic contactor on a rear side of an output filter for selecting the first current detector on the rear side of an output filter, a first current detector on a rear side of an output filter having a first current rating, a fourth reactor, and an output side electromagnetic contactor are respectively inserted in an electric path connecting each of the power conversion devices and the load and are connected in series from the power conversion devices to the load, and a series circuit is formed of a second current detector on a front side of an output filter having a second current rating smaller than the first current detector, a second reactor, and a second electromagnetic contactor on a front side of an output filter 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 on the front side of the output filter, a series circuit including an output filter front-side third current detector having a third current rating smaller than the first current detector, a third reactor, and an output filter front-side third electromagnetic contactor that selects the third current detector, an output filter capacitor connected between a common connection point of the filter front-side first electromagnetic contactor and the output filter rear-side first electromagnetic contactor and a negative pole end of the power conversion device, a series circuit including an output filter rear-side second electromagnetic contactor having a second current rating smaller than the first current detector and an output filter rear-side second electromagnetic contactor that selects the second current detector, the series circuits being connected in parallel between both ends of the output filter rear-side first electromagnetic contactor, and a series circuit including an output filter rear-side third current detector having a third current rating smaller than the second current detector and a output filter rear-side third electromagnetic contactor that selects the third current detector, a first electromagnetic contactor side AND circuit which takes a logical AND of a preset open / close setting 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 and a setting signal for permitting operation in a closed state 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; a second electromagnetic contactor side AND circuit which takes a logical AND of a preset open / close setting 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 a setting signal for permitting operation in a closed state 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; a third electromagnetic contactor side AND circuit which takes a logical AND of a preset open / close setting 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 and a setting signal for permitting operation in a closed state 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 side adder which adds up the number of times when each logical product result of the first to third electromagnetic contactor side logical product circuits is 1; an open / close setting side adder which adds up the number of times when the open / close setting signals of the first to third electromagnetic contactors are closed; a first comparator which outputs 1 only when the addition output of the operation permission setting side adder is equal to 1; and a second comparator which outputs 1 only when the addition output of the open / close setting side adder is equal to 1; a third comparator that outputs 1 when an absolute value of a difference between a voltage detection value obtained by detecting a voltage of the output filter capacitor and a voltage detection value obtained by detecting a voltage on a load side of the output side electromagnetic contactor is smaller than a set voltage judgment level; a load connection permission determination processing unit having a load connection permission signal generating AND circuit which takes a logical AND of the outputs of the first comparator to the third comparator and outputs a signal which permits load connection when a logical AND condition is satisfied; a second adder on the operation permission setting side which adds up the number of preset operation permission settings 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 output filter capacitor voltage control, 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 output filter capacitor voltage control, and 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, which are each permitted; and a fourth comparator which 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 an open / close setting 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 and a load connection permission signal; a second AND circuit that takes a logical AND of an open / close setting signal of the output filter front-side second electromagnetic contactor and the output filter rear-side second electromagnetic contactor and a load connection permission signal; a third AND circuit that takes a logical AND of an open / close setting 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 and a load connection permission signal; a fourth AND circuit which takes a logical AND of a signal obtained by logically inverting the load connection permission signal, an output signal of the fourth comparator, and an operation permission signal at 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 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, an output signal of the fourth comparator, and an operation permission signal at the output filter front-side second electromagnetic contactor and the output filter rear-side second electromagnetic contactor during the 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, an output signal of the fourth comparator, and an operation permission signal at 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 output filter capacitor voltage control; a first logical sum circuit that performs logical sum processing on the outputs of the first logical sum circuit and the fourth logical sum circuit and outputs 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; a second AND circuit that performs a logical OR operation on the outputs of the second AND circuit and the fifth AND circuit to output an opening / closing command for the output filter front-side second electromagnetic contactor and the output filter rear-side second electromagnetic contactor; a third AND circuit that performs a logical OR operation on the outputs of the third AND circuit and the sixth AND circuit 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; a first selection circuit that performs a logical sum operation on the outputs of the first, second, and third logical AND circuits, and outputs 0 when the result is 0, and outputs 1 when the result is 1; a second selection circuit that performs a logical sum operation on the outputs of the fourth, fifth, and sixth AND circuits, and outputs 0 when the result is 0, and outputs 1 when the result is 1; a switching command / current / voltage control permission signal generating unit having a current / voltage control permission signal generating adder that adds the outputs of the first selection circuit and the second selection circuit, and outputs, depending on a result of the addition, a current control permission signal of one of current control disallowance, current control, and output filter capacitor voltage control, and a voltage control permission signal of one of voltage control disallowance, voltage control, and output filter capacitor voltage control; a first AND circuit which takes a logical AND of an opening / closing command for the output filter front-side first electromagnetic contactor and the output filter rear-side first electromagnetic contactor output from the first OR circuit and an opening / closing state signal for the output filter front-side first electromagnetic contactor and the output filter rear-side first electromagnetic contactor; a second AND circuit which takes a logical AND of an opening / closing command for the output filter front-side second electromagnetic contactor and the output filter rear-side second electromagnetic contactor output from the second OR circuit and an opening / closing state signal for the output filter front-side second electromagnetic contactor and the output filter rear-side second electromagnetic contactor; a third AND circuit which takes a logical AND of 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 outputted from the third OR circuit and an opening / closing state 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; an output side electromagnetic contactor opening / closing command generating unit including: a first selector that outputs 1 when the load connection permission signal is permission and 0 when the load connection permission signal is not permission; and a fourth AND circuit that takes a logical AND between the output signal of the first selector and a signal resulting from a logical OR process of the outputs of the first to third AND circuits, and outputs an output side electromagnetic contactor opening / closing command; a voltage selection unit that selects output voltage detection when any of the output side electromagnetic contactors connected to the plurality of power conversion devices is in an open state when a voltage control permission signal specifying voltage control is output from the opening / closing command / current, voltage control permission signal generation unit, and selects a voltage command when all of the output side electromagnetic contactors are in a closed state; When the voltage control permission signal output from the switching command / current, voltage control signal generating unit specifies voltage control, a current command is generated by performing proportional control and integral control using a set proportional gain and integral gain so that the voltage detection value of the output filter capacitor becomes the voltage of the voltage command selected by the voltage selecting unit; When the voltage control permission signal specifies filter capacitor voltage control, a proportional control and an integral control are performed by the proportional gain and the integral gain so that a voltage detection value of an output filter capacitor becomes a detection value of an output voltage, thereby generating a current command; a voltage control unit including a voltage controller that switches a voltage command, a proportional gain, and an integral gain to zero when the voltage control permission signal specifies that voltage control is not permitted; a current range switching processing section including: a second selector which outputs 0 or 1 in response 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, outputs 0 or 2 in response 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 outputs 0 or 3 in response 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; an output filter front-side selector which has an adder which adds up outputs, and which selects one of the current detection values ​​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 which selects one of the current detection values ​​of the first to third current detectors on the rear side of the output filter in response to an output of the adder; When the current control permission signal generated by the switching command / current, voltage control permission generating unit is a current control, a proportional control and an integral control are performed by a proportional gain and an 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; When the current control permission signal is output filter capacitor voltage control, a proportional control and an integral control are performed by a proportional gain and an integral gain so that the current detection value selected by the current range switching processing unit becomes a current command value during the set output filter capacitor voltage control, thereby generating a voltage command for the power conversion device; A power conversion device comprising: a current controller that switches a current command, a proportional gain, and an integral gain to zero when the current control permission signal indicates that current control is not permitted.

2. 2. The power conversion device according to claim 1, further comprising: a current control selector that enables a current control input of the current controller when all output side electromagnetic contactors provided in a plurality of power conversion devices are in a closed state; and a command selector that selects a current control output current command when current control is selected by a control selection signal, and a voltage control output current command when voltage control is selected, and sets the selected current control input as the current control input of the current controller.

3. a voltage selection unit that selects output voltage detection when any of the output side electromagnetic contactors connected to the plurality of power conversion devices is in an open state when a voltage control permission signal specifying voltage control is output from the opening / closing command / current, voltage control permission signal generation unit, and selects a voltage command when all of the output side electromagnetic contactors are in a closed state; When the voltage control permission signal output from the opening / closing command / current, voltage control signal generating unit specifies voltage control, proportional control is performed using a proportional gain set under the condition that all of the output side electromagnetic contactors are in a closed state, and integral control is performed using an integral gain so that the voltage detection value of the load voltage becomes the voltage of the voltage command selected by the voltage selecting unit, and a load voltage compensation command is output when all of the output side electromagnetic contactors are in a closed state; When the voltage control permission signal specifies filter capacitor voltage control, proportional control is performed using a proportional gain and integral control is performed using an integral gain, which are set under the condition that all of the output side electromagnetic contactors are in a closed state, so that the detected value of the load voltage becomes the output voltage detected value selected by the voltage selection unit, and a load voltage compensation command is output when all of the output side electromagnetic contactors are in a closed state; a load voltage compensation control unit having a voltage command and a load voltage compensator for switching a proportional gain and an integral gain to zero when the voltage control permission signal specifies that voltage control is not permitted; 3. The power conversion device according to claim 1, further comprising: a superposition unit that superimposes a load voltage compensation command output from the load voltage compensator on a voltage command or an output voltage detection value input to a voltage controller of the voltage control unit.

4. 3. The power conversion device according to claim 1, further comprising: a reactor bypass electromagnetic contactor connected in parallel to a series assembly of the fourth reactor and the output side electromagnetic contactor; and an electromagnetic contactor opening and closing command generating unit that generates, based on an output side electromagnetic contactor opening and closing command output from a fourth AND circuit of the output side electromagnetic contactor opening and closing command generating unit, an opening and closing command to close the output side electromagnetic contactor and open the reactor bypass electromagnetic contactor, and an opening and closing command to open the output side electromagnetic contactor and close the reactor bypass electromagnetic contactor.

5. 4. The power conversion device according to claim 3, further comprising: a reactor bypass electromagnetic contactor connected in parallel to a series assembly of the fourth reactor and the output side electromagnetic contactor; and an electromagnetic contactor opening and closing command generating unit that generates, based on an output side electromagnetic contactor opening and closing command output from a fourth AND circuit of the output side electromagnetic contactor opening and closing command generating unit, an opening and closing command to close the output side electromagnetic contactor and open the reactor bypass electromagnetic contactor, and an opening and closing command to open the output side electromagnetic contactor and close the reactor bypass electromagnetic contactor.

6. 5. The power conversion device according to claim 4, further comprising a control selection unit which selects an opening / closing command to close the output side electromagnetic contactor and open the reactor bypass electromagnetic contactor when performing current control, and which selects an opening / closing command to open the output side electromagnetic contactor and close the reactor bypass electromagnetic contactor when performing voltage control.

7. 6. The power conversion device according to claim 5, further comprising a control selection unit which selects an opening / closing command to close the output side electromagnetic contactor and open the reactor bypass electromagnetic contactor when performing current control, and which selects an opening / closing command to open the output side electromagnetic contactor and close the reactor bypass electromagnetic contactor when performing voltage control.

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