JP2018107980A - Power converter and wind power generation system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter and wind power generation system for enabling power supply at the time of occurrence of abnormality and maintenance of a power transmission cable.SOLUTION: A power converter comprises: a first converter module group obtained by connecting output terminals of a plurality of converter modules in series; a second converter module group obtained by connecting output terminals of a plurality of converter modules in series; a central controller for controlling the plurality of converter modules; a parallel connection unit for connecting respective input terminals of the plurality of converter modules in parallel; a first output terminal connected to one end of an output terminal of the first module group; a neutral point terminal connected to the other end of the output terminal of the first module group and one end of an output terminal of the second module group; and a second output terminal connected to the other end of the output terminal of the second module group.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power converter that boosts the voltage of DC power and a wind power generation system using the same.

  In recent years, mass introduction of renewable energy such as solar power generation and wind power generation is expected. In wind power generation, development of a wind power generation system (wind farm) that includes a plurality of wind power generation devices and has a total generated power reaching several hundred MW is under consideration. The larger the total generated power of the wind power generation system, the larger the current collection system. In addition, such a large-scale wind power generation system is often installed on the coast or on the ocean, and the transmission distance tends to be long. And in such a large-scale wind power generation system installed in a remote place, there exists a problem that the transmission loss in a current collection system and a power transmission system is large.

  It is known that DC transmission has a smaller transmission loss than AC transmission. In order to apply direct current power transmission to a current collection and transmission system of a wind power generation system, it is necessary to convert alternating current power obtained by the rotational energy of the windmill into direct current power and further boost it to a predetermined voltage.

  As a technique related to this, Patent Document 1 describes a configuration of a power converter in which input terminals of a plurality of converter modules are connected in parallel and output terminals are connected in series, and a control method thereof.

Japanese Patent Laying-Open No. 2015-6066

  The power converter described in Patent Document 1 is a monopolar output, as is clear from FIG. 2 and the like of the same document, and the power converter must be stopped when an abnormality occurs in the output power transmission cable or during maintenance. I must. That is, in such a case, there is a problem that it is impossible to transmit all of the electric power generated by the wind power generation system.

  Moreover, generally the converter module which comprises a power converter carries the transformer. For the transformer, a composite dielectric using oil-impregnated insulating paper or polymer is used. When a DC electric field is applied to such a dielectric, space charges accumulate at the interface. The space charge causes local electric field distortion, which contributes to dielectric breakdown.

  The power converter described in Patent Document 1 achieves high voltage output by connecting output terminals of a plurality of converter modules in series. Since a DC high voltage is applied to the transformer mounted in the uppermost converter module for a long time, there is a concern that the above-mentioned insulation breakdown is a concern and it is difficult to maintain the long-term reliability of the device.

  Therefore, the present invention provides a power converter that does not require the output to be stopped when an abnormality occurs in the output power transmission cable or during maintenance while maintaining the long-term reliability of the device, and a wind power generation system using the power converter The purpose is to do.

  In order to solve the above problems, a power converter according to the present invention includes a first converter module group in which output terminals of a plurality of converter modules are connected in series, and a first converter module group in which output terminals of a plurality of converter modules are connected in series. Two converter module groups, a central control device that controls the plurality of converter modules, a parallel connection unit that connects in parallel the input terminals of the plurality of converter modules, and an output of the first module group A first output terminal connected to one end of the terminal; a neutral point terminal connecting the other end of the output terminal of the first module group; and an end of the output terminal of the second module group; And a second output terminal connected to the other end of the output terminal of the module group.

  According to the present invention, it is possible to provide a power converter that does not need to be stopped even when an abnormality occurs in an output destination power transmission cable or during maintenance.

1 is a diagram illustrating a power converter according to a first embodiment. It is a figure which shows the structural example of the converter module 10 which concerns on Example 1. FIG. FIG. 3 is a diagram illustrating a configuration example of a first converter unit 12 and a second converter unit 13 according to the first embodiment. FIG. 6 is a diagram illustrating another configuration example of the second converter unit 13 according to the first embodiment. The time is plotted on the horizontal axis, and the product of the voltage from the ground point of the secondary winding of the transformer 14 mounted on each converter module 10 and the generation time (voltage time product) is plotted on the vertical axis. FIG. 4 is a flowchart relating to replacement means for the converter module 10 in the central control device 40 according to the first embodiment. It is a block diagram of the several converter module 10 in the power converter 11 in the 1st output mode which concerns on Example 1. FIG. 3 is a configuration diagram of a plurality of converter modules 10 in the power converter 11 in the second output mode according to Embodiment 1. FIG. FIG. 6 is a diagram illustrating a power converter according to a second embodiment. It is a figure which shows the wind power generation system which concerns on Example 3. FIG. It is a figure which shows the wind power generation system which concerns on Example 4. FIG. FIG. 10 is a flowchart relating to replacement means for a converter module 10 in a central control device 40 and a farm control device 68 according to a fifth embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a power converter 11 according to the first embodiment. The power converter 11 includes a plurality of converter modules 10, an input terminal 30, an output terminal 31, and a central controller 40. A parallel connection 20 is provided between the input terminal 30 and the input side of the converter module 10, and the input side of each converter module 10 is connected in parallel via the parallel connection 20. Further, a series connection unit 21 is provided between the output terminal 31 and the output side of the converter module 10, and the output side of each converter module 10 is connected in series via the series connection unit 21. .

  The plurality of converter modules 10 are classified into a positive converter module group 33 and a negative converter module group 34. The positive-side converter module group 33 and the negative-side converter module group 34 each include, for example, n converter modules 10. In the following, for the sake of explanation, each of the converter modules 10 constituting the converter module group 33 on the positive side is referred to as converter modules P1, P2,..., Pn in order of the output voltage close to the ground voltage. Call it. Similarly, each converter module 10 constituting the negative-side converter module group 34 is referred to as converter modules N1, N2,..., Nn in order of the output voltage being close to the ground voltage.

  The output terminal 31 of the power converter 11 includes a positive voltage output terminal 311, a negative voltage output terminal 312, and a neutral point voltage terminal 313. The positive voltage output terminal 311 is connected to the higher voltage side of the output terminals of the converter module Pn. The negative voltage output terminal 312 is connected to the low voltage side of the output terminals of the converter module Nn. The neutral point voltage terminal 313 is connected to the low voltage side of the output terminals of the converter module P1 and the high voltage side of the output terminals of the converter module N1.

  The central control device 40 is connected to a later-described module control device 41 mounted in each converter module 10 in a wired or wireless manner, and performs calculation processing and module control necessary for controlling the operation of the power converter 11. Data exchange with the device 41 is performed.

  Normally, the central controller 40 gives a command to the module controller 41 in the converter module 10 so that the converter module 10 outputs a voltage higher than the input voltage. Since the output of each converter module 10 is connected in series, the output voltage of the power converter 11, that is, the voltage between the positive voltage output terminal 311 and the negative voltage output terminal 312 of the output terminal 31, is This is the sum of the output voltages of each converter module 10.

  Further, the power converter 11 includes a neutral point voltage terminal 313. By using this as a ground voltage, the power converter 11 can output a bipolar voltage of a positive voltage and a negative voltage. For example, the power converter 11 has ten converter modules 10, of which five belong to the positive converter module group 33 and the remaining five belong to the negative converter module group 34. . That is, the number n of converters included in one converter module group is assumed to be 5. In this case, for example, if the central controller 40 instructs each converter module 10 to output 40 kV, the output voltage of the power converter 11 is positive between the positive voltage output terminal 311 and the neutral point voltage terminal 313. 200 kV, and the voltage between the negative voltage output terminal 312 and the neutral point voltage terminal 313 is minus 200 kV.

  Further, when the central controller 40 gives different command values to the converter modules 10 belonging to the positive-side converter module group 33 and the negative-side converter module group 34, the power converter 11 has an absolute value. Different positive and negative voltages can be output. For example, when n = 5, the central controller 40 is 40 kV for the converter module 10 belonging to the positive-side converter module group 33, and for the converter module 10 belonging to the negative-side converter module group 34. Is given as a command value of 20 kV, the power converter 11 outputs plus 200 kV and minus 100 kV.

  Further, when the central controller 40 instructs the converter modules 10 belonging to the negative converter module group 34 to output 0 V, the output of the power converter 11 is only plus 200 kV, and the minus side is output. Since the output is 0 V, it can be considered that the output on the minus side is stopped.

  When the central control device 40 gives a command value of 0V to all the converter modules 10, the output of the power converter 11 is 0V on both the plus side and the minus side. In this case, the output of the power converter 11 can be regarded as stopped.

  As described above, the power converter 11 according to the present embodiment outputs a bipolar voltage and can arbitrarily control the output on the plus side and the minus side. Therefore, an abnormality has occurred in any of the power transmission cables connected to the output terminal 31. Even if it is time to maintain any of the transmission cables, the transmission of only the transmission cable in which an abnormality has occurred or the maintenance target transmission cable is stopped, and power transmission is performed by using other transmission cables. Redundancy that can be continued can be obtained.

  Note that the power transmission cable connected to the neutral point voltage terminal 313 may be omitted from the viewpoint of reducing the cable cost. In this case, the neutral point voltage terminal 313 is appropriately brought into contact with the ground or seawater, so that it can be regarded as a ground (seawater) return system using the ground or seawater as a return circuit.

  Next, a configuration example of the converter module 10 according to the first embodiment will be described with reference to FIG. The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. The converter module 10 includes a first converter unit 12, a second converter unit 13, a transformer 14, a module control device 41, an input section cutoff device 51, an output section cutoff device 52, and a module short circuit device 53. Is done. The first converter unit 12 converts the DC voltage applied between the input terminals 30 into an AC voltage and outputs the AC voltage. The transformer 14 boosts the AC voltage output from the first converter unit 12 in accordance with the turn ratio. Further, the second converter unit 13 rectifies the AC voltage boosted by the transformer 14 and outputs a DC voltage.

  Here, the connection of each component in the converter module 10 is demonstrated. The input terminal of the first converter unit 12 is connected to the parallel connection unit 20 via the input unit cutoff device 51. The output terminal of the second converter unit 13 is connected to the series connection unit 21 via the output unit cutoff device 52. The primary winding of the transformer 14 is connected to the output terminal of the first converter unit 12, and the secondary winding is connected to the input terminal of the second converter unit 13. The module short-circuit device 53 is connected between the output terminals of the converter module 10.

  In addition, the module control device 41 performs calculation processing necessary for controlling the operation of the converter module 10, and is connected to the central control device 40, the first converter unit 12, and the second converter unit 13. Implement data exchange. The data sent from the first converter unit 12 and the second converter unit 13 to the module control device 41 are, for example, instantaneous values of voltage and current. The data sent from the module control device 41 to the first converter unit 12 and the second converter unit 13 is, for example, a gate signal for driving the semiconductor switching element. Further, the module control device 41 can send a command to the input unit shut-off device 51, the output unit shut-off device 52, and the module short-circuit device 53 when an abnormality occurs. The input unit blocking device 51 connects or disconnects the parallel connection unit 20 in response to a command from the module control device 41. The output unit shut-off device 52 connects or disconnects the serial connection unit 21 in response to a command from the module control device 41. The module short-circuit device 53 opens or short-circuits the output terminal of the converter module 10 in response to a command from the module control device 41.

  FIG. 3 shows a configuration example of the first converter unit 12 and the second converter unit 13 of FIG. As shown here, the first converter unit 12 is a two-level full-bridge inverter circuit composed of a bridge circuit composed of four semiconductor switching elements 15 such as IGBTs and four diodes 16 and a capacitor 17. is there. Specifically, the bridge circuit included here includes a series connection circuit in which a diode is connected in antiparallel to each of two semiconductor switching elements 15 connected in series, and the output terminal of both circuits is a transformer. 14 is connected to both ends of the primary winding. With such a configuration, the first converter unit 12 can be driven by the phase shift method, and the switching loss of the semiconductor switching element 15 can be greatly reduced.

  On the other hand, the second converter unit 13 is composed of a bridge circuit composed of, for example, four diodes 16 and a capacitor 17. Specifically, in this bridge circuit, a series connection circuit of two diodes 16 is installed in parallel, and input terminals of both circuits are connected to both ends of the secondary winding of the transformer 14. Since the diode 16 is lower in cost than the semiconductor switching element 15 and is a passive component, a driving circuit can be omitted, so that the second converter unit 13 can be configured at low cost.

  FIG. 4 shows another configuration example of the second converter unit 13 of FIG. The first converter unit 12 shown here is the same as that shown in FIG. The second converter unit 13 is a two-level full-bridge converter circuit including a bridge circuit including a semiconductor switching element 15 such as four IGBTs and four diodes 16 and a capacitor 17. Specifically, the bridge circuit included here includes a series connection circuit in which diodes are connected in antiparallel to each of two semiconductor switching elements 15 connected in series, and the input terminals of both circuits are transformers. 14 are connected to both ends of the secondary winding. By doing in this way, the power converter 11 can interchange electric power bidirectionally. Further, by driving the second converter unit 13 by the synchronous rectification method, the conduction loss can be reduced as compared with the case where rectification is performed by the bridge circuit composed of four diodes shown in FIG.

  Specific examples of the first converter unit 12 and the second converter unit 13 of the present embodiment have been shown in FIGS. 3 and 4, but the combination of the converter units is not limited to these. For example, the same effect as that of the present embodiment can be obtained by any combination of a three-level half-bridge type, three-level full-bridge type inverter circuit, converter circuit, and rectifier circuit.

  Next, with respect to the transformer 14 of FIG. 2, a method of suppressing the generation of space charge and preventing insulation deterioration will be described. As shown in FIG. 1, the power converter 11 realizes a high voltage output by connecting output terminals of a plurality of converter modules 10 in series. Therefore, for example, the secondary winding of the transformer 14 mounted on the converter module Pn which is the uppermost converter module 10 includes a plurality of lower converters in addition to the voltage output by the converter module Pn itself. The output voltage of the module 10 is superimposed. Here, since the generation amount of space charge depends on the product of the magnitude of the DC voltage and the application time thereof, the product of the voltage from the ground point of the secondary winding of each transformer 14 and the generation time thereof. By exchanging the configuration of each converter module 10 so that (voltage time product) changes in the vicinity of zero, generation of space charge can be suppressed and insulation deterioration can be prevented.

  This specific method will be described with reference to FIG. FIG. 5 shows the time on the horizontal axis, and the product of the voltage from the ground point of the secondary winding of the transformer 14 mounted on each converter module 10 and the generation time (voltage time product) on the vertical axis. FIG. Before the electrical connection of the converter module 10 is replaced, the first output mode is referred to, and after the replacement is referred to as the second output mode.

  In the first output mode, each voltage time product (solid line) in the converter modules P1 to Pn belonging to the positive-side converter module group 33 increases in proportion to the time, and the negative-side converter module group 34 Each of the voltage time products (broken lines) in the converter modules N1 to Nn belonging to 1 decreases in proportion to time. On the other hand, also in the second output mode, each voltage-time product (solid line) in the converter modules P1 to Pn belonging to the positive-side converter module group 33 increases in proportion to the time, and the negative-side converter module group. 34. The point that each voltage time product (broken line) in the converter modules N1 to Nn belonging to 34 decreases in proportion to the time is common to the first output mode, but each voltage time after the start of the second output mode. The product is changing towards zero.

  The switching of the output mode is performed, for example, at a timing when the voltage-time product of the converter module Pn reaches the threshold value VTth. At this timing, the electrical connection of the converter module 10 is switched, and the converter on the positive side is switched. The module group 33 and the negative converter module group 34 are replaced.

  Replacement of the electrical connection of the converter module 10 is performed by replacing, among the plurality of converter modules 10, the converter modules 10 having the same absolute value and opposite signs. That is, the connection is switched so that the converter modules P1 and N1 and the converter modules P2 and N2 are interchanged. When this is generalized, the connection is switched so that the converter modules Pn and Nn are interchanged with each other. By repeating such module replacement, the voltage-time product of each converter module 10 is adjusted so as to shift in the vicinity of zero (in the range of −VTth to + VTth), so that generation of space charge can be suppressed. it can. In addition, when the transformer 14 is an oil immersion transformer, a phenomenon is known in which oil and an insulator are charged by the flow of oil. If such a charged state continues, partial discharge occurs and contributes to the failure of the transformer. However, such a flow charging phenomenon can be suppressed by controlling as shown in FIG.

  FIG. 6 is a flowchart used when the central controller 40 in FIG. 1 determines the output mode change in FIG. When the power converter 11 is activated, the central controller 40 starts a replacement determination process for the converter module 10 and first executes the first output mode (step S01). Next, the central controller 40 determines whether or not it is necessary to stop due to the occurrence of an abnormality (step S31). If it is determined that the power converter 11 needs to be stopped (Yes), the flowchart of the replacement determination process is ended and the power converter 11 is stopped. On the other hand, if it is determined that it is not necessary to stop the power converter 11 (No), the process proceeds to step S10.

  In step S10, the central controller 40 calculates the voltage-time product of the converter module Pn. In step S11, the central controller 40 performs the first threshold determination process, and if it is determined that the voltage-time product of the converter module Pn has become larger than the threshold VTth (Yes), the second output is performed in step S12. After switching to the mode, the process proceeds to step S32. On the other hand, if it is determined that the voltage-time product is equal to or less than the threshold value VTth (No), the first output mode is continued (step S13) and the process returns to step S31.

  When the second output mode is switched in step S12, it is determined in step 32 whether or not it is necessary to stop. Since step S32 is the same as step S31, description thereof is omitted. If no abnormality has occurred, the central controller 40 calculates the voltage-time product of the converter module Pn as in step S10 (step S20). In step S21, if the central controller 40 performs the second threshold value determination process and determines that the voltage-time product of the converter module Nn has become smaller than the threshold value -VTth (Yes), the first control is performed in step S22. After switching to the output mode, the process returns to step S31. On the other hand, if it is determined that the voltage-time product is equal to or greater than the threshold −VTth (No), the second output mode is continued (step S23) and the process returns to step S32.

  In the flowchart of FIG. 6, the first output mode is first executed in step S01, but the second output mode may be executed first. In that case, in the steps after step S01, the first and second output modes need to be interchanged. Moreover, although the example which calculates the voltage time product of the converter module Pn was demonstrated in step S10, S20, the voltage time product of the other one converter module 10 may be calculated, and several converter module Ten voltage-time products may be calculated. Further, when the voltage is known, only the output time may be calculated. In that case, the threshold determination after step S10 is performed not on the voltage time product but on the output time. When calculating the voltage / time product of the plurality of converter modules 10, a plurality of threshold determinations may be executed in steps S11 and S12, or the voltage / time product of the plurality of converter modules 10 may be calculated. You may perform threshold determination with respect to a comprehensive voltage time product.

  Next, a specific configuration for replacing the converter module 10 will be described with reference to FIGS. 7A and 7B. 7A and 7B show the configurations of the plurality of converter modules 10 in the power converter 11 in the first output mode and the second output mode, respectively. In order to replace the converter module 10 described above, a plurality of switchgears 22 provided in the series connection unit 21 are used. Each switchgear 22 opens and shorts both terminals of the switchgear 22 in response to a command from the central controller 40. Thereby, the positive voltage output terminal 311, the negative voltage output terminal 312, and the neutral point voltage terminal 313 constituting the output terminal 31 and the output terminals of the positive converter module group 33 and the negative converter module group 34 are connected. Can be switched.

  For example, in the first output mode, each switching device 22 is connected as shown in FIG. 7A, so that the upper converter module group becomes a positive converter module group 33 that outputs a positive voltage, and the lower converter module group The converter module group becomes a negative-side converter module group 34 that outputs a negative voltage. On the other hand, in the second output mode, each switching device 22 is connected as shown in FIG. 7B, so that the upper converter module group becomes the negative converter module group 34 that outputs a negative voltage, and the lower converter module group 34 The converter module group becomes a positive-side converter module group 33 that outputs a positive voltage.

  As described above, in the power converter 11 of the present embodiment, by switching the plurality of switching devices 22 shown in FIGS. 7A and 7B, the position of each converter module 10 is not changed, and the positive side The electrical connection between the module group 33 and the negative module group 34 can be switched, and the switching can be automated using the central controller 40. As a result, the above-described suppression of space charge generation and the suppression of fluid charging phenomenon can be realized.

  Furthermore, as shown in FIGS. 7A and 7B, the positive output terminal (+) of each converter module 10 is arranged next to the negative output terminal (−) of the adjacent converter module 10, so that The electrical wiring in the converter module group becomes linear, and the wiring structure can be simplified.

  7A and 7B show an electrical connection structure and do not show an actual wiring configuration. Actually, the wiring can be configured three-dimensionally. For example, in FIG. 7A and FIG. 7B, the positive voltage output terminal 311 and the negative voltage output terminal 312 are arranged on the left side, and the neutral point voltage terminal 313 is arranged on the right side. It is also possible to combine them in one place. Such wiring is effective when the power converter 11 is housed in a narrow space such as in a tower of a wind turbine generator.

  Next, the power converter 11 of Example 2 is demonstrated using FIG. In addition, the same code | symbol is attached | subjected to the part already demonstrated in Example 1, and the description is abbreviate | omitted.

  As described with reference to FIG. 2 and the like, in the first embodiment, one converter unit (second converter unit 13) is provided on the secondary side of the transformer 14 in the converter module 10. In the converter module 10, a plurality of converter units are provided on the secondary side of the multi-winding transformer 18 provided in place of the transformer 14, and they are connected in series so that each converter module 10 A higher voltage can be output. Hereinafter, the structure of the converter module 10 of a present Example is demonstrated in detail.

  As described above, the multi-winding transformer 18 of the present embodiment has a secondary winding divided into a plurality of parts, and in FIG. 8, an example of a secondary winding divided into two as an example. Is shown. The two secondary windings of the multi-winding transformer 18 are connected to the second converter unit 13 and the third converter unit 19, respectively. The output terminal of the second converter unit 13 and the output terminal of the third converter unit 19 are respectively connected to the series connection part 21 of the power converter 11 via the output part cutoff device 52, respectively. By connecting the negative output terminal (−) of the converter unit 13 and the positive output terminal (+) of the third converter unit 19, the second converter unit 13 and the third converter unit 19 are connected. This constitutes a series circuit. The two module short-circuit devices 53 are connected so that the output terminals of the second converter unit 13 and the third converter unit 19 can be short-circuited, respectively.

  As described above, the converter module 10 according to the second embodiment is provided with a plurality of converter units in the secondary winding of the multi-winding transformer 18, so that the converter module 10 according to the second embodiment is higher than the converter module 10 according to the first embodiment. Can output voltage. Alternatively, when the output voltage of the power converter 11 may be equal to that of the first embodiment, the second embodiment can output the same voltage with a smaller number of converter modules 10 than the first embodiment. This contributes to cost reduction and volume reduction of the converter 11. At this time, since the withstand voltage required for the semiconductor switching element 15, the diode 16, the capacitor 17 and the like constituting the second converter unit 13 and the third converter unit 19 is reduced, inexpensive general-purpose products can be applied. Contributes to cost reduction. Further, depending on the breakdown voltage required for these parts, a plurality of elements may be connected in series to improve the breakdown voltage. Such a configuration causes a decrease in reliability due to variations in element characteristics. In some cases, additional components, functions, or control means are used to improve the reliability. In this case, the cost of the power converter 11 increases. If the multi-winding transformer 18 according to the second embodiment is used, in the second converter unit 13 and the third converter unit 19, it is not necessary to use components in which elements are connected in series. Thereby, the reliability of the converter module 10 and by extension, the power converter 11 improves.

  Due to the presence of the multi-winding transformer 18, the converter module 10 has a plurality of output terminals. Even in such a case, the converter module 10 described in FIGS. 7A and 7B of the first embodiment is replaced. The method can be applied and the same effect can be obtained. Since a specific method can be easily inferred from the description of the first embodiment, duplicate description is omitted.

  Note that the AC voltage output from the first converter unit 12 is preferably a high frequency equal to or higher than the commercial frequency, for example, 1 kHz. By doing so, the multi-winding transformer 18 is excited at a high frequency, and the volume can be reduced. Further, by forming a wound core formed by winding a plurality of thin strip-shaped magnetic materials around the iron core of the multi-winding transformer 18, it is possible to suppress the occurrence of eddy current loss that is prominent in a high-frequency region. The volume of the vessel 18 can be further reduced. As such a wound iron core, a ribbon-like alloy having an amorphous structure or a fine crystal structure mainly composed of iron is preferable, but not limited thereto. These measures are particularly effective when the power converter 11 is housed in a narrow space such as in a tower of a wind power generator.

  FIG. 9 shows an embodiment of a wind power generation system 66 to which the power converter 11 is applied. Here, a large-scale wind power generation system 66 installed on an offshore platform will be described as an example, but the wind power generation system 66 may be installed on land such as a coast. As shown in FIG. 9, the wind power generation system 66 includes a plurality of wind power generation devices 65, a farm control device 68 that controls them, a high-voltage DC cable 72 (HVDC) that is a power transmission cable corresponding to a high voltage of 100 kV or higher, and the like. It consists of The wind power generator 65 can be roughly classified into power generation facilities and power conversion facilities. Among these, the power generation facilities include a windmill 61, a gear 62, a generator 63 that generates AC power, and the like. The power conversion equipment includes a power conditioner 64 that converts generated AC power into DC power, a power converter 11, and the like. The power conditioner 64 and the power converter 11 are accommodated in the tower 67. By doing in this way, manufacture of the wind power generator 65 becomes easy, and the gravity center of the wind power generator 65 becomes low, and it can give allowance for the mechanical strength of the tower 67.

  The power converter 11 has been described in the first or second embodiment, boosts the DC power output from the power conditioner 64, and outputs positive and negative voltages and a neutral point voltage. The plurality of wind turbine generators 65 are connected in parallel via the high-voltage DC cable 72. By setting it as such a structure, the wind power generation system 66 can collect the output electric power of the several wind power generator 65, and can transmit to the land. Further, the wind power generation system 66 includes a farm control device 68 that comprehensively controls each wind power generation device 65, the power converter 11, and the like, thereby improving the power generation amount and reducing the current collection loss. 65 and an extended function such as protection coordination of the power converter 11 can be provided.

  On the remote land, an AC / DC converter 73 for connecting to the power system 74 is installed, whereby the DC voltage transmitted from the wind power generation system 66 is converted into AC and supplied to the power system 74. be able to.

  If the power converter 11 of the present embodiment is used, the high-voltage DC cable 72 that can be normally used is used even when an abnormality occurs in any of the high-voltage DC cables 72 or a part of the AC / DC converter 73 or during maintenance. Since power transmission can be continued, it is possible to provide a wind power generation system that does not require the output to be stopped.

  In addition, in a wind power generation system installed on the ocean, a power transmission cable is laid on the seabed. Therefore, when AC power is transmitted, loss due to charging and discharging of the cable parasitic capacitance occurs. If the power converter 11 is applied, since direct current can be transmitted, such loss does not occur and high efficiency is achieved.

  It is also possible to configure a wind power generation system group by installing a plurality of wind power generation systems 66. Even in such a case, the power converter 11 of the present embodiment is suitable. Further, in the present embodiment, as an example, it is assumed that the wind power generation system 66 is installed on the ocean, but it may be installed on land. When the wind power generation system 66 is installed on land, the power converter 11 of the present embodiment is suitable particularly when the wind power generation system 66 is large-scale.

  FIG. 10 shows another embodiment of the wind power generation system 66 to which the power converter 11 is applied. The parts already described are given the same reference numerals, and the description thereof is omitted. The wind power generation system 66 of the present embodiment includes a plurality of wind power generation devices 65, a medium voltage DC cable 71 (MVDC), a high voltage DC cable 72, a medium voltage DC-high voltage DC converter 75, and the like. The plurality of wind power generators 65 are connected in parallel via a medium-voltage DC cable 71 and connected to a medium-voltage DC-high-voltage DC converter 75 installed on the offshore platform.

  The medium-voltage DC-high-voltage DC converter 75 further boosts the output voltage of the plurality of wind power generators 65 and is connected to a land-based AC / DC converter 73 via a high-voltage DC cable 72. Here, the medium-voltage direct current and the high-voltage direct current are, for example, from several tens kV to one hundred kV and one hundred kV or more.

  By adopting such a configuration, the power converter 11 housed in each wind turbine generator only needs to have a relatively low insulating property, and therefore the power converter 11 can be expected to be reduced in size and cost. . If the power converter 11 of the present embodiment is used, it is not necessary to stop the output even when an abnormality occurs in the medium voltage DC cable 71, the high voltage DC cable 72, the medium voltage DC-high voltage DC converter 75, or during maintenance. A wind power generation system can be provided.

  Next, the wind power generation system 66 of Example 5 is demonstrated using FIG. In the fifth embodiment, a method for replacing the converter module 10 executed jointly by the farm controller 68 and the central controller 40 included in the wind power generation system 66 of the third or fourth embodiment will be described. The points already described in the flowchart etc. will be omitted, and the description will focus on the differences from FIG.

  In step S11 shown in the flowchart of FIG. 11, if the central controller 40 of each power converter 11 performs the first threshold value determination process and determines that the voltage-time product has become larger than the threshold value VTth (Yes). The farm control device 68 that controls the wind power generation system 66 performs the process of step S51. On the other hand, if it is determined in step S11 that the voltage-time product is equal to or less than the threshold value VTth (No), the central controller 40 performs the process of step S13.

  In step S51, if the farm controller 68 performs the first generated power determination process and determines that the total generated power of the wind power generation system 66 is equal to or less than a predetermined value (Yes), the central controller 40 performs step. The process of S12 is performed. On the other hand, if it is determined in step S51 that the total generated power is larger than the predetermined value (No), the central controller 40 performs the process of step S13.

  Similarly, in step S21, if the central controller 40 performs the second threshold value determination process and determines that the voltage-time product has become smaller than the threshold value -VTth (Yes), the firmware controller 68 determines in step S52. Process. On the other hand, if it is determined in step S21 that the voltage-time product is equal to or greater than the threshold value −VTth (No), the central controller 40 performs the process of step S23.

  In step S52, the farm control device 68 performs the second generated power determination process in the same manner as in step S51, and determines that the total generated power of the wind power generation system 66 is equal to or less than a predetermined value (Yes). The central controller 40 performs the process of step S22. On the other hand, if it is determined in step S52 that the total generated power is larger than the predetermined value (No), the central controller 40 performs the process of step S23.

  In this way, the wind power generation system 66 can replace the converter module 10 only during a period when the total power generation amount is small, and prohibit the replacement of the converter module 10 during a period when the total power generation amount is large. In order to reverse the positive and negative outputs of the power converter 11 by replacing the converter module 10, each power converter 11 needs to stop the output. If the output of each power converter 11 is stopped during a period when the total power generation amount of the wind power generation system 66 is large, many power generation opportunities are lost. According to the fifth embodiment, the loss of power generation opportunities is minimized. And the wind power generation system 66 which also ensured the long-term reliability of the power converter 11 can be provided.

  In the first and second generated power determination processes in steps S51 and S52, a total generated power amount, a predicted value of the total generated power, a predicted value of the total generated power amount, or the like may be used. By using these factors in combination, it is possible to reduce the loss of power generation opportunities of the wind power generation system 66.

  Further, when the wind power generation system 66 is expected to generate power stably over a long period of time, it is assumed that the timing for replacing the converter module 10 is lost for a while and the voltage-time product deviates greatly from the vicinity of zero. The Such a case can be dealt with by appropriately changing the threshold values used in the first and second threshold determinations and the threshold values used in the first and second generated power determinations.

  The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. A part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  For example, the semiconductor switching element 15 shown in FIG. 3 includes a semiconductor switching element group configured by connecting a plurality of semiconductor switching elements in series and in parallel. The same applies to other components.

  In each embodiment, control lines and information lines indicate what is considered necessary for the explanation, and not all control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

10: Converter module 11: Power converter 12: First converter unit 13: Second converter unit 14: Transformer 15: Semiconductor switching element 16: Diode 17: Capacitor 18: Multi-winding transformer 19: Third converter unit 20: parallel connection unit 21: series connection unit 22: switchgear 30: input terminal 31: output terminal 311: positive voltage output terminal 312: negative voltage output terminal 313: neutral point voltage terminal 32: contact Point 33: Positive converter module group 34: Negative converter module group 40: Central controller 41: Module controller 51: Input blocker 52: Output blocker 53: Module short circuit 61: Windmill 62 : Gear 63: Generator 64: Power conditioner 65: Wind power generator 66: Wind power generator system 67: Tower 68: Farm controller 71: Medium pressure Flow Cable 72: high-voltage direct current cable 73: AC-DC converter 74: power system 75: Medium 圧直 flow - high voltage direct current converter

Claims (13)

A first converter module group in which output terminals of a plurality of converter modules are connected in series;
A second converter module group in which output terminals of a plurality of converter modules are connected in series;
A central controller for controlling a plurality of said converter modules;
A parallel connection part for connecting the input terminals of the plurality of converter modules in parallel;
A first output terminal connected to one end of the output terminal of the first module group;
A neutral point terminal connecting the other end of the output terminal of the first module group and one end of the output terminal of the second module group;
A second output terminal connected to the other end of the output terminal of the second module group;
A power converter comprising: The power converter according to claim 1, wherein
By the command of the central controller,
The power converter characterized by stopping output of both or any one of the first output terminal and the second output terminal. The power converter according to claim 1 or 2,
The central controller is
A first output mode in which the first converter module group outputs a positive voltage and the second converter module group outputs a negative voltage;
The power converter, wherein the first converter module group outputs a negative voltage, and the second converter module group switches between a second output mode in which a positive voltage is output. The power converter according to claim 3, wherein
The output terminals of the plurality of converter modules are respectively connected in series via a switching device,
When executing the first output mode, the plurality of switchgears are short-circuited or opened to output positive voltage and negative voltage to the first and second converter module groups, respectively.
When executing the second output mode, the plurality of switchgears are opened or shorted to output negative voltage and positive voltage to the first and second converter module groups, respectively. vessel. The power converter according to claim 4, wherein
The central controller is
Sequentially calculating the voltage-time product of the output voltage and output time of the converter module;
When the voltage time product is greater than the positive first threshold, switching from the first output mode to the second output mode,
A power converter that switches from the second output mode to the first output mode when the voltage-time product becomes smaller than a second threshold with a negative sign. The power converter according to any one of claims 1 to 5,
The converter module is
DC / AC conversion means for converting a DC voltage into an AC voltage;
A transformer for boosting the AC output voltage of the DC / AC conversion means;
AC / DC conversion means for converting the AC output voltage boosted by the transformer into a DC voltage, and
The power converter is an oil immersion transformer. The power converter according to any one of claims 1 to 5,
The converter module is
DC / AC conversion means for converting a DC voltage into an AC voltage;
A transformer for boosting the AC output voltage of the DC / AC conversion means;
AC / DC conversion means for converting the AC output voltage boosted by the transformer into a DC voltage, and
The transformer includes a plurality of secondary windings, and the AC / DC conversion means is provided in the same number as the secondary windings. The power converter according to any one of claims 1 to 5,
The converter module is
DC / AC conversion means for converting a DC voltage into an AC voltage;
A transformer for boosting the AC output voltage of the DC / AC conversion means;
AC / DC conversion means for converting the AC output voltage boosted by the transformer into a DC voltage, and
The transformer is excited at a frequency higher than the commercial frequency,
The iron core of the transformer is a wound iron core configured by winding a plurality of thin strip-shaped magnetic materials,
A power converter comprising an amorphous structure containing iron as a main component or a ribbon-shaped alloy having a fine crystal structure. The power converter according to any one of claims 1 to 5,
The converter module is
DC / AC conversion means for converting a DC voltage into an AC voltage;
A transformer for boosting the AC output voltage of the DC / AC conversion means;
AC / DC conversion means for converting the AC output voltage boosted by the transformer into a DC voltage, and
The DC / AC conversion means is composed of either a two-level full bridge inverter circuit comprising a switching element such as an IGBT and a diode, a three level full bridge inverter circuit, or a three level half bridge inverter circuit. It is characterized by. Power converter. The power converter according to any one of claims 1 to 5,
The converter module is
DC / AC conversion means for converting a DC voltage into an AC voltage;
A transformer for boosting the AC output voltage of the DC / AC conversion means;
AC / DC conversion means for converting the AC output voltage boosted by the transformer into a DC voltage, and
The AC / DC conversion means is a two-level full bridge converter circuit comprising a switching element such as an IGBT and a diode, a three level half bridge converter circuit, a three level full bridge converter circuit, or a rectifier circuit comprising a diode. A power converter, comprising: A plurality of wind power generators;
A plurality of wind power generators connected in parallel, and a high-voltage DC cable for transmitting generated power to a remote location;
A farm control device for controlling the plurality of wind turbine generators;
A wind power generation system comprising:
Each of the wind power generators
A generator that generates AC power by rotating a windmill;
A power conditioner that converts the AC power into DC power;
The power converter according to any one of claims 1 to 10, wherein the DC power is boosted.
A tower housing the power conditioner and the power converter;
A wind power generation system comprising: A plurality of wind power generators;
A plurality of wind turbine generators connected in parallel, medium voltage DC cable for transmitting generated power;
A medium voltage DC-high voltage DC converter that boosts and outputs the power supplied from the medium voltage DC cable;
A high-voltage DC cable for transmitting the power output by the medium-voltage DC-high-voltage DC converter to a remote location;
A farm control device for controlling the plurality of wind power generators and the medium-voltage DC-high-voltage DC converter;
A wind power generation system comprising:
Each of the wind power generators
A generator that generates AC power by rotating a windmill;
A power conditioner that converts the AC power into DC power;
The power converter according to any one of claims 1 to 10, wherein the DC power is boosted.
A tower housing the power conditioner and the power converter;
A wind power generation system comprising: A plurality of wind power generators;
A high-voltage DC cable for transmitting the power generated by the plurality of wind turbine generators to a remote location;
A farm control device for controlling the plurality of wind turbine generators;
A wind power generation system comprising:
Each of the wind power generators
A generator that generates AC power by rotating a windmill;
A power conditioner that converts the AC power into DC power;
The power converter according to any one of claims 3 to 5, wherein the DC power is boosted.
A tower housing the power conditioner and the power converter;
It has
The farm control device
When the total generated power of the plurality of wind turbine generators is a predetermined value or less,
A wind power generation system, wherein each power converter is allowed to switch between the first output mode and the second output mode.

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