Power conversion device

Abstract

To make a cross flow suppression compatible with a current response in a multi-device juxtaposition configuration where power conversion devices each including a plurality of current detectors of different ratings are connected in parallel.SOLUTION: A plurality of power conversion devices 1 and 2 are provided in parallel with a load 200. The power conversion device comprises: a first current detector HCT_A11, a first reactor L_A11, and a first electromagnetic contactor MC11 which selects the first current detector, which are interposed in a cable run connecting e.g., the power conversion device 1 and the load 200 and successively connected in series from the power conversion device 1 to the load 200. The power conversion device comprises: a second current detector HCT_A21 of which the current rating is different, a second reactor L_A21, and a second electromagnetic contactor MC21 which selects the second current detector, which are connected in serial between a common connection point of HCT_A11 and L_A11 and a common connection point of MC11 and the load 200.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a multiple-unit parallel configuration in which power conversion devices having multiple current detectors (hereinafter sometimes referred to as HCTs) with different ratings are connected in parallel in order to control current with high precision. [Background technology]

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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).

[0007] 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.

[0008] 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.

[0009] 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. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2021-180533 A Summary of the Invention [Problem to be solved by the invention]

[0011] In the method of Patent Document 1, parallel operation of multiple power converters is applied when the system load exceeds the rated load per power converter. When devices are connected in parallel, a current (hereinafter referred to as a cross current) flows between the devices according to the error in the output voltage. To suppress the cross current, reactors L11 and L12 are connected between the devices.

[0012] The current rating when operating with HCT_11 and HCT_12 is current rating A, and the current rating when operating with HCT_21 and HCT_22 is current rating B. Assume that current rating A has a larger current value than current rating B.

[0013] In other words, when the load amount in Figure 2 is large and the load current value is large, it switches to current rating A, and when the load amount is small and the load current value is small, it switches to current rating B.

[0014] Cross current can be defined by the following equation (1). di = (V × dt) / L … (1) Here, V is the DC voltage of the power conversion device, dt is the output voltage pulse error time between the devices, and L is the inductance of the reactor.

[0015] For example, suppose you want to suppress the cross current to about 10% of the rated current. In this case, the inductance value of the cross current suppression reactor will be larger if you suppress it to current rating B, which has a smaller current rating (in order to suppress it to current rating B, it is necessary to increase L, which is the denominator in equation (1)).

[0016] In such devices, a current response may be required. The inductance value required to satisfy the current response is given by the following formula (2). L = (dt × V) / di…(2) Here, V is the voltage difference between the output voltage of the power conversion device and the load voltage, dt is the required response time, and di is the amount of change in current.

[0017] As a result, the inductance value required to satisfy the requirements for current rating A, which has a larger current rating, is smaller than that for current rating B (Equation (2) shows that L must be small). Thus, in the case of equipment with multiple current ratings, it is clear that there is a challenge in simultaneously suppressing cross currents and meeting current response requirements.

[0018] The issues with operating multiple units by simply combining the outputs of the conventional technology are summarized below. When multiple units have current ratings, a method of combining the outputs using a reactor for cross-current suppression is applied to connect the devices in parallel, which is a known technology. In this case, it is difficult to achieve both cross-current suppression and current response.

[0019] The present invention is intended to solve the above-mentioned problems, and its object is to provide a power conversion device that can achieve both cross-current suppression and current response in a multiple-unit parallel configuration in which power conversion devices having multiple current detectors with different ratings are connected in parallel. [Means for solving the problem]

[0020] In order to solve the above problem, the power conversion device according to claim 1 is a first current detector having a first current rating, a first reactor having a first inductance value, and a first electromagnetic contactor for selecting the first current detector; the first current detector being inserted in an electric path connecting each of the power conversion devices to the load and sequentially connected in series from the power conversion device to the load; The power supply circuit is characterized by comprising: a second current detector having a second current rating smaller than that of the first current detector, a second reactor having a second inductance value, and a second electromagnetic contactor for selecting the second current detector, all connected in series between a common connection point of the first current detector and the first reactor and a common connection point of the first electromagnetic contactor and a load.

[0021] The power conversion device according to claim 2 comprises: a first current detector having a first current rating, which is inserted in an electric path connecting each of the power conversion devices to the load and is connected in series from the power conversion device to the load, a first electromagnetic contactor for selecting the first current detector, and a first reactor having a first inductance value; The power conversion system is characterized by comprising: a second current detector having a second current rating smaller than that of the first current detector, connected in series between a common connection point of the first current detector and the first electromagnetic contactor and a common connection point of the first electromagnetic contactor and the first reactor; a second electromagnetic contactor for selecting the second current detector; and a second reactor set to a second inductance value that can suppress cross currents between a plurality of power conversion devices by a total inductance value with a first inductance value of the first reactor when the second current detector is selected.

[0022] The power conversion device according to claim 3 comprises: The power conversion system includes a plurality of power conversion devices provided in parallel with a load, a first current detector having a first current rating, a first reactor having a first inductance value, a first electromagnetic contactor for selecting the first current detector and for disconnecting the load, the first current detector being inserted in an electric circuit connecting each of the power conversion devices and the load and connected in series from the power conversion devices to the load, a second current detector having a second current rating smaller than that of the first current detector and connected in series between a common connection point of the first reactor and the first electromagnetic contactor and a common connection point of the first electromagnetic contactor and the load, a second reactor set to a second inductance value that can suppress cross current between the plurality of power conversion devices by the total inductance value with the first inductance value of the first reactor when the second current detector is selected, and a second electromagnetic contactor for selecting the second current detector and for disconnecting the load. Effect of the Invention

[0023] (1) According to the inventions described in claims 1 to 3, the inductance values ​​of the first and second reactors for cross current suppression can be appropriately set for each current rating, making it possible to suppress cross current suppression for each current rating, and suppressing a decrease in the response of the current flowing through the load when operating by selecting a first current detector having a higher current rating than the second current detector. (2) According to the invention as set forth in claim 3, in a case where power running is the main application, the load can be protected when the power conversion device stops due to a failure. [Brief description of the drawings]

[0024] [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. 1 is a configuration diagram of a power conversion device according to a first embodiment of the present invention. [Figure 4] FIG. 11 is a configuration diagram of a power conversion device according to a second embodiment of the present invention. [Diagram 5] FIG. 11 is a configuration diagram of a power conversion device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiment. There is a demand for a power conversion device with a 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. As a prerequisite for the present invention, the following circuit configuration will be described.

[0026] 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

[0027] FIG. 3 shows a main circuit configuration of the power conversion device in the first embodiment.

[0028] In Figure 3, multiple power conversion devices 1 and 2 are provided in parallel with a load 200, and in an electric circuit connecting the power conversion device 1 and the load 200, a first current detector HCT_A11 having a first current rating, a first reactor L_A11 having a first inductance value, and a first electromagnetic contactor MC11 that selects the first current detector HCT_A11 are connected in series in this order from the power conversion device 1 to the load 200.

[0029] Between the common connection point of HCT_A11 and the first reactor L_A11 and the common connection point of MC11 and the load 200, there are connected in series 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.

[0030] As described above, between the power conversion device 2 and the load 200, a first current detector HCT_A12, a first reactor L_A12, and a first electromagnetic contactor MC12 are connected in series in sequence from the power conversion device 2 to the load 200, and a second current detector HCT_A22, a second reactor L_A22, and a second electromagnetic contactor MC22 are connected in series between the common connection point of HCT_A12 and the reactor L_A12 and the common connection point of MC12 and the load 200.

[0031] In Figure 3, the current rating when operating with HCT_A11 and HCT_A12 is current rating A, and the current rating when operating with HCT_A21 and HCT_A22 is current rating B. Assume that current rating A has a larger current value than current rating B. To improve the accuracy of current detection, different current detectors HCTs are used depending on current ratings A and B.

[0032] In addition, the circuit is configured to separate the reactors used for current rating A and current rating B. It has L_A11 and L_A12 as cross-current suppression reactors for current rating A. L_A11 and L_A12 are installed on the circuit when MC11 and MC12 are closed. It has L_A21 and L_A22 as cross-current suppression reactors for current rating B. L_A21 and L_A22 are installed on the circuit when MC21 and MC22 are closed.

[0033] When operating at rated current A, that is, when MC11 and MC12 are closed, reactors L_A11 and L_A12 are present on the circuit between power conversion devices 1, 2 and load 200. Since L_A21 and L_A22 are not on the circuit, they have no effect on controlling the cross current or the load current. The reactor values ​​of L_A11 and L_A12 are set to suppress the cross current for current rating A.

[0034] When operating at current rating B, i.e. when MC21 and MC22 are closed, reactors L_A21 and L_A22 are present on the circuit between power conversion devices 1, 2 and load 200. Because L_A11 and L_A12 are not on the circuit, they do not affect the control of cross currents or load currents. The reactor values ​​of L_A21 and L_A22 are set to suppress cross currents for current rating B. In this way, the inductance value can be set appropriately to suppress cross currents for each current rating, making it possible to suppress a decrease in the current response of load 200 when operating at current rating A. EXAMPLES

[0035] Fig. 4 shows a main circuit configuration of a power conversion device in Example 2. In Fig. 4, a plurality of power conversion devices 1 and 2 are provided in parallel with a load 200, and a first current detector HCT_A11 having a first current rating, a first electromagnetic contactor MC11 that selects the first current detector HCT_A11, and a first reactor L_B11 having a first inductance value are sequentially connected in series from the power conversion device 1 to the load 200 in an electric path that connects the power conversion device 1 and the load 200.

[0036] Connected in series between both ends of MC11 are 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.

[0037] As described above, between the power conversion device 2 and the load 200, a first current detector HCT_A12, a first electromagnetic contactor MC12, and a first reactor L_B12 are connected in series in sequence from the power conversion device 2 to the load 200, and a second current detector HCT_A22, a second reactor L_A22, and a second electromagnetic contactor MC22 are connected in series between both ends of the MC12.

[0038] Furthermore, as described below, the second inductance values ​​of the second reactors L_A21, L_A22 are set to a second inductance value that can suppress cross currents between multiple power conversion devices by using a total inductance value together with the first inductance values ​​of the first reactors L_B11, L_B12 when the second current detectors HCT_A21, HCT_A22 are selected.

[0039] 4, the current rating when operating with HCT_A11 and HCT_A12 is designated as current rating A, and the current rating when operating with HCT_A21 and HCT_A22 is designated as current rating B. It is assumed that current rating A has a larger current value than current rating B.

[0040] In FIG. 4, a circuit is configured having reactors (L_B11, L_B12) applied to the respective circuits with current ratings A and B, and reactors (L_A21, L_A22) applied to current rating B.

[0041] When operating at rated current A, i.e. when MC11 and MC12 are closed, reactors L_B11 and L_B12 are present on the circuit of power conversion devices 1 and 2 and load 200. Since L_A21 and L_A22 are not present on the circuit, they have no effect on controlling the cross current or the load current. The reactor values ​​of L_B11 and L_B12 are set to suppress the cross current for current rating A.

[0042] During operation at rated current B, i.e., when MC21 and MC22 are closed, reactors L_A21, L_A22, L_B11, and L_B12 are present on the circuit of the power conversion devices 1, 2 and the load 200. The inductance values ​​of the second reactors L_A21 and L_A22 are set to suppress cross current for rated current B, in combination with the inductance values ​​of the first reactors L_B11 and L_B12. For this reason, the inductance values ​​are smaller than those in the first embodiment.

[0043] In the configuration of Example 2, since the inductance value can be appropriately set to suppress cross current for each current rating, it is possible to suppress a decrease in the current response of the load during operation at the current rating A. Since the inductance values ​​of L_A21 and L_A22 can be made smaller than those in Example 1, it is possible to reduce the reactor size. EXAMPLES

[0044] Fig. 5 shows a main circuit configuration of a power conversion device in Example 3. In Fig. 5, a plurality of power conversion devices 1 and 2 are provided in parallel with a load 200, and 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 for selecting the first current detector HCT_A11 are sequentially connected in series from the power conversion device 1 to the load 200 in an electric path connecting the power conversion device 1 and the load 200.

[0045] Connected in series between both ends of MC11 are 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.

[0046] As described above, between the power conversion device 2 and the load 200, a first current detector HCT_A12, a first reactor L_A12, and a first electromagnetic contactor MC12 are connected in series in sequence from the power conversion device 2 to the load 200, and a second current detector HCT_A22, a second reactor L_A22, and a second electromagnetic contactor MC22 are connected in series between both ends of the MC12.

[0047] 5, the current rating (first current rating) when operating with HCT_A11 and HCT_A12 is designated as current rating A, and the current rating (second current rating) when operating with HCT_A21 and HCT_A22 is designated as current rating B. It is assumed that current rating A has a larger current value than current rating B.

[0048] In FIG. 5, a circuit is configured with reactors (L_A11, L_A12) applied to the respective circuits for current rating A and current rating B, and reactors (L_A21, L_A22) applied to current rating B. L_A11 and L_A12 are provided as cross-current suppression reactors applied to current rating A and current rating B. L_A11 and L_A12 are provided on the circuit when MC11 and MC12 are closed and when MC21 and MC22 are closed. The difference from the second embodiment is that L_A11 and L_A12 are provided on the power conversion device side as viewed from the MC. L_A21 and L_A22 are provided as cross-current suppression reactors for current rating B. L_A21 and L_A22 are provided on the circuit when MC21 and MC22 are closed.

[0049] Furthermore, as described below, the second inductance values ​​of the second reactors L_A21, L_A22 are set to a second inductance value that can suppress cross currents between multiple power conversion devices by using a total inductance value together with the first inductance values ​​of the first reactors L_A11, L_A12 when the second current detectors HCT_A21, HCT_A22 are selected.

[0050] When operating at rated current A, i.e. when MC11 and MC12 are closed, reactors L_A11 and L_A12 are present on the circuit of power conversion devices 1 and 2 and load 200. Since L_A21 and L_A22 are not on the circuit, they have no effect on controlling the cross current or the load current. The reactor values ​​of L_A11 and L_A12 are set to suppress the cross current for current rating A.

[0051] During operation at rated current B, i.e., when MC21 and MC22 are closed, reactors L_A21, L_A22, L_A11, and L_A12 are present on the circuit of the power conversion devices 1, 2 and the load 200. The inductance values ​​of the second reactors L_A21 and L_A22 are set to suppress cross current for rated current B, in combination with the inductance values ​​of the first reactors L_A11 and L_A12. For this reason, the inductance values ​​are smaller than those in the first embodiment.

[0052] In the configuration of Example 3, the inductance value can also be set appropriately to suppress cross current for each current rating, so that it is possible to suppress a decrease in the current response of the load during operation at the current rating A. Since the inductance values ​​of L_A21 and L_A22 can be made smaller than those in Example 1, it is possible to reduce the reactor size.

[0053] Here, consider the case where a fault occurs during power running. In this case, even if the power conversion devices 1 and 2 stop, the current flowing through the reactor is not cut off instantly but continues to flow to the load side. In the case of FIG. 5, an electromagnetic contactor MC is provided between the reactor and the load 200. When the power conversion devices stop, the MC is opened and disconnected. This prevents current from flowing to the load 200 when the power conversion device breaks down. For example, if an overvoltage occurs in the load and the power conversion device is stopped, the load 200 may be damaged if the current flowing through the reactor continues to flow to the load. If the current can be interrupted by disconnecting the MC as described above, damage to the load can be prevented.

[0054] The present invention is not limited to the parallel connection of two units, but can also be applied to the case where three or more power conversion devices are connected in parallel to a load and operated. [Explanation of symbols]

[0055] 1, 2...Power conversion device 200…load HCT_A11, HCT_A12, HCT_A21, HCT_A22…Current detector MC11, MC12, MC21, MC22...Magnetic contactor L_A11, L_A12, L_B11, L_B12, L_A21, L_A22...Reactors

Claims

1. a first current detector having a first current rating, a first reactor having a first inductance value, and a first electromagnetic contactor for selecting the first current detector; the first current detector being inserted in an electric path connecting each of the power conversion devices to the load and sequentially connected in series from the power conversion device to the load; A power conversion device comprising: a second current detector having a second current rating smaller than that of the first current detector, a second reactor having a second inductance value, and a second electromagnetic contactor that selects the second current detector, all connected in series between a common connection point of the first current detector and a first reactor and a common connection point of the first electromagnetic contactor and a load.

2. a first current detector having a first current rating, the first current detector being inserted in an electric path connecting each of the power conversion devices to the load and sequentially connected in series from the power conversion device to the load; a first electromagnetic contactor selecting the first current detector; and a first reactor having a first inductance value; A power conversion device comprising: a second current detector having a second current rating smaller than that of the first current detector, connected in series between a common connection point of the first current detector and the first electromagnetic contactor and a common connection point of the first electromagnetic contactor and the first reactor; a second electromagnetic contactor that selects the second current detector; and a second reactor that is set to a second inductance value that can suppress cross currents between a plurality of power conversion devices by a total inductance value with a first inductance value of the first reactor when the second current detector is selected.

3. a first current detector having a first current rating, which are respectively inserted in an electric path connecting each of the power conversion devices and the load and connected in series from the power conversion devices to the load; a first reactor having a first inductance value; a first electromagnetic contactor for selecting the first current detector and for disconnecting the load; a second current detector having a second current rating smaller than that of the first current detector, which is connected in series between a common connection point of the first reactor and the first electromagnetic contactor and a common connection point of the first electromagnetic contactor and the load; a second reactor set to a second inductance value that can suppress cross current between the plurality of power conversion devices by a total inductance value with the first inductance value of the first reactor when the second current detector is selected; and a second electromagnetic contactor for selecting the second current detector and for disconnecting the load.

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