DC power distribution system

Abstract

The DC power distribution system of the present invention suppresses the increase in equipment costs by disconnecting the power distribution line that has a short-circuit fault from the output path. It includes: multiple power conversion devices (41, 42), a DC bus (60), multiple power distribution lines, multiple first current cut-off sections (11, 12) respectively connected to the input side of the multiple power conversion devices, multiple second current cut-off sections (21, 22) respectively connected between the multiple power conversion devices and the DC bus, and multiple third current cut-off sections (31, 32, 33) respectively provided on the multiple power distribution lines. The cut-off current value of the multiple third current cut-off sections is set to a value smaller than the maximum allowable current value of the power conversion device to which the short-circuit current reaches the maximum allowable current value in the shortest time.

Description

Technical Field

[0001] This application relates to DC power distribution systems. Background Technology

[0002] A DC distribution system is known that distributes power from multiple power systems to multiple DC loads. This DC distribution system uses power conversion devices with AC-DC or DC-DC conversion functions to convert power from the input AC or DC power system into DC power, and then distributes this DC power to distribution lines connected to the DC loads. In such a DC distribution system, when a short-circuit fault occurs in the distribution line, it is necessary to electrically isolate that distribution line from the output path.

[0003] In conventional DC power distribution systems, circuit breakers are installed in the power distribution lines, and current resonant circuits are incorporated into the power conversion devices. In such DC power distribution systems, when a short-circuit fault occurs in the power distribution lines, the current resonant circuit of the power conversion device generates a zero current, causing the circuit breaker installed on the power distribution lines to operate, thus electrically isolating the power distribution lines from the output path (for example, see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-29044 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] However, in traditional DC power distribution systems, the current resonant circuit of the power conversion device needs to have the capacity to withstand the large short-circuit current generated during a short-circuit fault, which leads to the problem of an increased current resonant circuit size. When the current resonant circuit size increases, the equipment cost of the power conversion device rises.

[0009] This application was made to solve the above-mentioned problems, and its purpose is to suppress the increase in equipment costs in a DC power distribution system that can electrically isolate the power distribution line from the output path when a short-circuit fault occurs in the power distribution line.

[0010] Technical means for solving technical problems

[0011] The DC power distribution system of this application includes: multiple power conversion devices that convert power supplied from multiple power systems into DC power and output it; a DC bus through which the DC power output from the multiple power conversion devices flows; multiple distribution lines that branch off from the DC bus; multiple first current interruption units connected between the multiple power systems and the multiple power conversion devices; multiple second current interruption units connected between the multiple power conversion devices and the DC bus; and multiple third current interruption units disposed on the multiple distribution lines. Furthermore, the interruption current value of the multiple third current interruption units is set to a value smaller than the maximum permissible current value of the power conversion devices to which the short-circuit current in the multiple power conversion devices reaches the maximum permissible current value of the power conversion devices in the shortest possible time.

[0012] Invention Effects

[0013] In the DC power distribution system of this application, the cutting current value of multiple third current cutting-off sections is set to a value smaller than the maximum allowable current value of the power conversion device when the short-circuit current in multiple power conversion devices reaches the maximum allowable current value of the power conversion device in the shortest time. Therefore, in the event of a short-circuit fault in the power distribution line, the power distribution line can be electrically isolated from the output path, and the increase in equipment cost can be suppressed. Attached Figure Description

[0014] Figure 1 This is a structural diagram of the DC power distribution system according to Implementation Method 1.

[0015] Figure 2 This is an explanatory diagram showing a short-circuit fault in the DC power distribution system of Embodiment 1.

[0016] Figure 3 This is an explanatory diagram showing a short-circuit fault in the DC power distribution system of Embodiment 2.

[0017] Figure 4 This is a structural diagram of the power conversion device involved in Embodiment 3.

[0018] Figure 5 This is a structural diagram of the power conversion device involved in Embodiment 3.

[0019] Figure 6 This is a structural diagram of the power conversion device involved in Embodiment 4.

[0020] Figure 7 This is a structural diagram of the power conversion device involved in Embodiment 5.

[0021] Figure 8This is a structural diagram of the power conversion device involved in Embodiment 6.

[0022] Figure 9 This is a structural diagram of the power conversion device according to Embodiment 7.

[0023] Figure 10 This is a structural diagram of the power conversion device according to Embodiment 7. Detailed Implementation

[0024] The DC power distribution system according to the embodiments of this application will now be described in detail with reference to the accompanying drawings. Furthermore, the same reference numerals in the drawings indicate the same or equivalent parts.

[0025] Implementation method 1.

[0026] Figure 1 This is a structural diagram illustrating the DC power distribution system of Embodiment 1. In this embodiment, an example of a DC power distribution system that receives power from two power systems and distributes that power to three DC loads will be described. Figure 1 As shown, in the DC power distribution system 10 of this embodiment, power conversion devices 41 and 42 receive power input from multiple power systems 1 and 2, respectively, and distribute the power to multiple DC loads 51, 52, and 53. Furthermore, in the DC power distribution system of this embodiment, there can be three or more power systems and four or more DC loads.

[0027] The first current cutoff section 11 is connected to the input side of the power conversion device 41, and the second current cutoff section 21 is connected to the output side of the power conversion device 41. The first current cutoff section 12 is connected to the input side of the power conversion device 42, and the second current cutoff section 22 is connected to the output side of the power conversion device 42. The output of the power conversion device 41 is connected to the DC bus 60 via the second current cutoff section 21. The output of the power conversion device 42 is connected to the DC bus 60 via the second current cutoff section 22. DC loads 51, 52, and 53 are connected to the DC bus 60 via the third current cutoff sections 31, 32, and 33, respectively.

[0028] Power conversion device 41 receives power from power system 1 via first current cutoff unit 11. Furthermore, power conversion device 41 converts the power received from power system 1 into DC power with different voltage levels, and then outputs it to DC bus 60 via second current cutoff unit 21. Power conversion device 42 receives power from power system 2 via first current cutoff unit 12. Furthermore, power conversion device 42 converts the power received from power system 2 into DC power with different voltage levels, and then outputs it to DC bus 60 via second current cutoff unit 22. The power input to DC bus 60 is distributed to DC loads 51, 52, and 53 via third current cutoff units 31, 32, and 33, respectively.

[0029] In this embodiment, power conversion devices 41 and 42 are either DC-DC power conversion devices or AC-DC power conversion devices. For example, if power system 1 is a DC system, power conversion device 41 is a DC-DC power conversion device. Furthermore, if power system 2 is an AC system, power conversion device 42 is an AC-DC power conversion device. Power conversion devices 41 and 42 are power conversion devices composed of semiconductor elements.

[0030] Furthermore, in this embodiment, the first current interruption units 11 and 12, the second current interruption units 21 and 22, and the third current interruption units 31, 32, and 33 can be current interruptors such as semiconductor circuit breakers with semiconductor elements, fuseless circuit breakers that interrupt the current path by opening and closing mechanical contacts, and fuses that interrupt the current path by Joule heating the conductor when a large current flows. Appropriate circuit breakers are selected considering the interruption time required by the DC power distribution system 10, the current value to be interrupted, cost, etc.

[0031] The DC power distribution system 10 configured in this way receives power from multiple power systems 1 and 2 respectively, converts the received power into DC power through power conversion devices 41 and 42, and then distributes the DC power to DC loads 51, 52, and 53 respectively. Therefore, even if any of the power systems 1 and 2 experiences a power outage, the DC power distribution system 10 can still receive power from the other power system and continue to distribute power to the DC loads.

[0032] Next, the operation of the DC power distribution system 10 in this embodiment when a short-circuit fault occurs will be explained.

[0033] Figure 2 This diagram illustrates a short-circuit fault occurring in a power distribution line connected to a DC load in the DC power distribution system 10 of this embodiment. Figure 2In the diagram, the solid arrow indicates the location where the short-circuit fault 70 occurs. Additionally, the two dashed arrows show the short-circuit current 71 flowing from power system 1 to the location of the short-circuit fault 70 and the short-circuit current 72 flowing from power system 2 to the location of the short-circuit fault, respectively.

[0034] like Figure 2 As shown, in the DC power distribution system 10, a short-circuit fault 70 is assumed to occur in the power distribution line connected to the DC load 51. At this time, the short-circuit current 71 flowing from the power system 1 flows into the location of the short-circuit fault 70 via the first current cut-off section 11, the power conversion device 41, the second current cut-off section 21, the DC bus 60, and the third current cut-off section 31. Similarly, the short-circuit current 72 flowing from the power system 2 flows into the location of the short-circuit fault 70 via the first current cut-off section 12, the power conversion device 42, the second current cut-off section 22, the DC bus 60, and the third current cut-off section 31. Therefore, the short-circuit currents 71 and 72 pass through the power conversion devices 41 and 42, and the third current cut-off section 31, respectively.

[0035] The short-circuit current 71 flows until any one of the current-cutting sections 11, 21, and 31 is activated. Similarly, the short-circuit current 72 flows until any one of the current-cutting sections 12, 22, and 31 is activated. Therefore, during the period from the occurrence of a short-circuit fault to the interruption of the short-circuit current 71, the short-circuit current 71 flows in the power conversion device 41. Similarly, during the period from the occurrence of a short-circuit fault to the interruption of the short-circuit current 72, the short-circuit current 72 flows in the power conversion device 42.

[0036] Furthermore, the short-circuit currents 71 and 72 largely depend on parasitic impedances such as parasitic inductance and parasitic resistance present in the current path, as well as the configuration of the power conversion devices 41 and 42. However, in typical DC power distribution systems, the parasitic impedance of the current path, which is a cause of power loss, is designed to be relatively small in order to efficiently distribute power to the DC load. Therefore, the effect of the parasitic impedance of the current path on the short-circuit current is almost negligible. Additionally, power conversion devices come in various configurations, and in the case of a power conversion device containing an inductor, the magnitude of the short-circuit current is reduced. Moreover, the inductance value of the power conversion device varies depending on the configuration of the power conversion device 42; therefore, the inductance value of power conversion device 41 differs from that of power conversion device 42. Consequently, the value of the short-circuit current 71 differs from the value of the short-circuit current 72.

[0037] The semiconductor elements constituting a power conversion device have a maximum allowable current. Generally, if a current exceeding this maximum allowable current flows, the likelihood of semiconductor element failure increases. Therefore, the maximum allowable current of the power conversion device is referred to as the maximum allowable current value. Furthermore, during the period from the occurrence of a short-circuit fault until the operation of any one of the first current cutoff sections 11, 12, the second current cutoff sections 21, 22, and the third current cutoff section 31, the short-circuit currents 71 and 72 increase over time.

[0038] Here, it is assumed that the inductance inside power conversion device 41 is greater than the inductance inside power conversion device 42. Therefore, the short-circuit current 72 flowing through power conversion device 42 increases faster than the short-circuit current 71 flowing through power conversion device 41. Consequently, the time it takes for the short-circuit current 72 flowing through power conversion device 42 to reach its maximum permissible current value is shorter than that of the short-circuit current 71. Therefore, compared to power conversion device 41, power conversion device 42 has a lower tolerance for short-circuit faults.

[0039] To ensure the reliability of the DC power distribution system, electrical isolation of the distribution line experiencing a short-circuit fault is required at a current value lower than the maximum permissible current value of the power conversion device with the lowest short-circuit fault tolerance among the power conversion devices included in the DC power distribution system. Specifically, the interruption current values ​​of the multiple third current interruption sections 31, 32, and 33 are set to be lower than the maximum permissible current value of the power conversion device among the multiple power conversion devices 41 and 42, where the short-circuit current reaches the maximum permissible current value of the power conversion device in the shortest possible time.

[0040] In this DC power distribution system 10, even in the event of a short-circuit fault, the third current cut-off unit can disconnect only the faulty power line from the output path, allowing power to continue to be distributed to other normal power lines, thus preventing the power conversion devices 41 and 42 from malfunctioning. Furthermore, since the power conversion devices 41 and 42 do not require a current resonant circuit, the increase in equipment cost can be suppressed.

[0041] Implementation method 2.

[0042] In Embodiment 1, the setting of the cutting-off current value of the third current cutting-off unit was explained. In Embodiment 2, the setting of the cutting-off current value of the second current cutting-off unit was explained. Furthermore, the structure of the DC power distribution system in this embodiment is the same as the structure of the DC power distribution system in Embodiment 1.

[0043] Figure 3This diagram illustrates a scenario where a short-circuit fault occurs in the DC bus 60 of the DC power distribution system 10 according to this embodiment. In this case, the short-circuit current 71 flowing from the power system 1 passes through the first current cutoff section 11, the power conversion device 41, the second current cutoff section 21, and the DC bus 60, and flows into the location where the short-circuit fault 70 occurs. Similarly, the short-circuit current 72 flowing from the power system 2 passes through the first current cutoff section 12, the power conversion device 42, the second current cutoff section 22, and the DC bus 60, and flows into the location where the short-circuit fault 70 occurs. Therefore, the short-circuit currents 71 and 72 pass through the power conversion devices 41 and 42, respectively.

[0044] The short-circuit current 71 flows until either the first current cut-off section 11 or the second current cut-off section 21 is activated. Similarly, the short-circuit current 72 flows until either the first current cut-off section 12 or the second current cut-off section 22 is activated. Therefore, during the period from the occurrence of a short-circuit fault until the short-circuit current 71 is cut off, the short-circuit current 71 flows through the power conversion device 41. Similarly, during the period from the occurrence of a short-circuit fault until the short-circuit current 72 is cut off, the short-circuit current 72 flows through the power conversion device 42.

[0045] Here, in order to interrupt the short-circuit currents 71 and 72 and protect the power conversion devices 41 and 42 through the second current interruption units 21 and 22, the interruption current value of the second current interruption unit 21 needs to be set to a value less than the maximum allowable current value of the power conversion device 41. Similarly, the interruption current value of the second current interruption unit 22 needs to be set to a value less than the maximum allowable current value of the power conversion device 42. That is to say, the interruption current values ​​of the second current interruption units 21 and 22 need to be set separately, taking into account the short-circuit fault tolerance of the power conversion devices 41 and 42. However, when multiple second current interruption units are set to different interruption current values, the cost of the DC power distribution system may increase due to the increase in the types of equipment constituting the DC power distribution system.

[0046] In the DC power distribution system 10 of this embodiment, by making the power conversion devices 41 and 42 have the same tolerance to short-circuit faults, the second current cut-off units 21 and 22 can be set to the same cut-off current value. As a result, since the equipment used for the second current cut-off units 21 and 22 can be interchangeable, the cost increase of the DC power distribution system 10 can be suppressed.

[0047] As a method to ensure that the power conversion devices 41 and 42 have the same short-circuit fault tolerance, for example, the internal inductance value of the power conversion device with the lower tolerance can be increased, or the semiconductor elements constituting the power conversion devices 41 and 42 can be semiconductor elements with a larger maximum allowable current value. Furthermore, in this embodiment, "same" includes errors caused by individual differences between the devices constituting the power conversion devices 41 and 42.

[0048] In this DC power distribution system, since the equipment used in the second current cut-off section is interchangeable, cost increases can be suppressed. Furthermore, by ensuring that the power conversion devices 41 and 42 have the same short-circuit fault tolerance, the third current cut-off section can also be interchangeable with the equipment used in the second current cut-off section, thus further suppressing cost increases.

[0049] Implementation method 3.

[0050] In Embodiment 3, the case where one power system in the DC power distribution system of Embodiment 1 is a three-phase AC system and the other power system is a single-phase AC system will be described. Furthermore, the structure of the DC power distribution system in this embodiment is the same as that of the DC power distribution system in Embodiment 1, except that power system 1 is a three-phase AC system and power system 2 is a single-phase AC system.

[0051] Figure 4 This is a structural diagram of the power conversion device 41 of the DC power distribution system according to this embodiment. The power conversion device 41 is an AC-DC power conversion device used to receive three-phase AC power from the power system 1 and convert it into DC power. Figure 4 As shown, the power conversion device 41 of this embodiment includes an AC input terminal 410 for inputting three-phase AC power into the power system 1, a transformer 411, a filter circuit 412, a rectifier 413, and a DC output terminal 414 for outputting DC power.

[0052] Transformer 411 includes a primary winding and a secondary winding. The turns ratio of the primary and secondary windings is determined by the relationship between the DC voltage of the DC distribution system, the AC voltage of the primary winding, and the AC voltage of the secondary winding. Furthermore, the primary winding of transformer 411 includes taps to ensure that the voltage of the secondary winding remains constant when the voltage of power system 1 fluctuates. Since rectifier 413 does not have output voltage control, if the voltage of power system 1 fluctuates and the voltage of the secondary winding also fluctuates, the voltage of the DC distribution system will also fluctuate. If the DC voltage in the DC distribution system fluctuates outside the operating voltage range of the DC load, the DC load will be unable to operate. In this embodiment, the power conversion device 41 has taps on its primary winding, thus keeping the voltage of the secondary winding constant. Therefore, the output of the DC distribution system 10 is not affected by voltage fluctuations in power system 1, improving the reliability of the DC distribution system.

[0053] In order to prevent harmonics generated by rectifier 413 from flowing into power system 1, filter circuit 412 is connected, and filter circuit 412 is connected as needed.

[0054] The rectifier 413 includes six diodes D11 to D16 as semiconductor elements. Typically, Figure 4 The rectifier 413 shown is also called a 6-pulse rectifier or simply a diode rectifier. Furthermore, to suppress voltage ripple from the DC output terminal 414, a DC reactor or capacitor is sometimes connected between the rectifier 413 and the DC output terminal 414. Additionally, the current capacity of the power conversion device 41 can be increased by connecting multiple rectifiers 413 in parallel, and the current capacity can also be increased by connecting multiple diodes D11 to D16 in parallel as needed.

[0055] Furthermore, transformer 411 has a short-circuit impedance, which can suppress short-circuit current in the event of a short-circuit fault. Moreover, by setting this short-circuit impedance to an appropriate value, the short-circuit current can be suppressed below the maximum permissible current value of the semiconductor element.

[0056] Figure 5 This is a structural diagram of the power conversion device 42 of the DC power distribution system according to this embodiment. This power conversion device 42 is an AC-DC power conversion device used to receive single-phase AC power from the power system 2 and convert it into DC power. Figure 5 As shown, the power conversion device 42 of this embodiment includes an AC input terminal 420 for inputting single-phase AC power into the power system 2, a transformer 421, a filter circuit 422, a rectifier 423, and a DC output terminal 424 for outputting DC power.

[0057] Transformer 421 includes a primary winding and a secondary winding. The turns ratio of the primary and secondary windings is determined by the relationship between the DC voltage of the DC distribution system, the AC voltage of the primary winding, and the AC voltage of the secondary winding. Furthermore, the primary winding of transformer 421 includes taps so that the voltage of the secondary winding remains constant when the voltage of the power system 2 changes. Since rectifier 423 does not have an output voltage control function, if the voltage of the power system 2 changes and the voltage of the secondary winding also changes, the voltage of the DC distribution system will also change. If the DC voltage in the DC distribution system changes to outside the operating voltage range of the DC load, the DC load will be unable to operate. In this embodiment, the power conversion device 42 has taps on its primary winding, thus keeping the voltage of the secondary winding constant. Therefore, the output of the DC distribution system 10 is not affected by voltage fluctuations in the power system 2, improving the reliability of the DC distribution system.

[0058] A filter circuit 422 is connected to prevent harmonics generated by rectifier 423 from flowing into power system 2, and the filter circuit 422 is connected as needed.

[0059] The rectifier 423 includes four diodes D21 to D24 as semiconductor elements. Typically, Figure 5 The rectifier 423 shown is also called a single-phase rectifier or simply a diode rectifier. Furthermore, to suppress voltage ripple from the DC output terminal 424, a DC reactor or capacitor is sometimes connected between the rectifier 423 and the DC output terminal 424. Additionally, the current capacity of the power conversion device 42 can be increased by connecting multiple rectifiers 423 in parallel, and the current capacity can also be increased by connecting multiple diodes D21 to D24 in parallel as needed.

[0060] Furthermore, transformer 421 has a short-circuit impedance, which can suppress short-circuit current in the event of a short-circuit fault. Moreover, by setting this short-circuit impedance to an appropriate value, the short-circuit current can be suppressed below the maximum permissible current value of the semiconductor element.

[0061] In a DC power distribution system 10 configured in this way, where one power system is a three-phase AC system and the other is a single-phase AC system, the received AC power can be converted into DC power and distributed to DC loads.

[0062] Implementation method 4.

[0063] In Embodiment 3, the case where the rectifier of the power conversion device 42 is a single-phase rectifier was described. However, since the harmonic components output by a single-phase rectifier are generally more than those of a 6-pulse rectifier, the filter circuit 422 of the power conversion device 42 needs to be larger than the filter circuit 412 of the power conversion device 41, which may increase the cost of the DC power distribution system. In addition, since the ripple of the output voltage of a single-phase rectifier is greater than that of a 6-pulse rectifier, the capacitance of the capacitor used to suppress the output voltage ripple needs to be larger. Therefore, this leads to an increase in the cost of the DC power distribution system. The DC power distribution system of Embodiment 4 is the same as that of Embodiment 3, except that the rectifier of the power conversion device 42, which receives single-phase AC power, is a single-phase PWM rectifier (single-phase pulse width modulation rectifier). In addition, the structure of the DC power distribution system in this embodiment is the same as that of the DC power distribution system in Embodiment 1, with power system 1 being a three-phase AC system and power system 2 being a single-phase AC system.

[0064] Figure 6 This is a structural diagram of the power conversion device 42 of the DC power distribution system according to this embodiment. This power conversion device 42 is an AC-DC power conversion device used to receive single-phase AC power from the power system 2 and convert it into DC power. Figure 6 As shown, the power conversion device 42 of this embodiment includes an AC input terminal 420 for inputting single-phase AC power from the power system 2, a transformer 421, a filter circuit 422, a rectifier 423, and a DC output terminal 424 for outputting DC power. Furthermore, in the power conversion device 42 of this embodiment, a capacitor 425 for suppressing output voltage ripple is connected in parallel with the DC output terminal 424. The transformer 421 is the same as that of the power conversion device 42 of Embodiment 3, and the filter circuit 422 is also connected as needed.

[0065] The rectifier 423 in this embodiment is obtained by replacing the four diodes D21 to D24 of the rectifier 423 of the power conversion device 42 in embodiment 3 with four semiconductor switching elements Q21 to Q24. Typically, Figure 6The rectifier 423 shown is referred to as a single-phase PWM rectifier. Semiconductor switching elements Q21 to Q24 can be IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors) with self-arching capabilities, where diodes are connected in reverse parallel. Multiple elements can be connected in parallel to increase current capacity as needed. Furthermore, semiconductor switching elements Q21 to Q24 are switched on and off via a gate drive circuit (not shown), and this switching action (switching operation) is controlled by a control signal sent from a control unit (not shown).

[0066] Since the rectifier 423 in this embodiment is composed of a single-phase PWM rectifier, harmonic components output through the switching operations of semiconductor switching elements Q21 to Q24 can be suppressed, thus enabling the miniaturization of the filter circuit 422. Furthermore, by performing the switching operations of semiconductor switching elements Q21 to Q24 at a higher frequency, the filter circuit 422 can be miniaturized. Additionally, since the ripple of the DC voltage output through the switching operations of semiconductor switching elements Q21 to Q24 can be reduced, the capacitor 425 can be miniaturized.

[0067] Furthermore, given the stringent requirements for power quality and the low permissible harmonics in the single-phase AC system of power system 2, the power conversion device 42 that supplies power to power system 2 needs to employ a single-phase PWM rectifier.

[0068] Furthermore, in the DC power distribution system of this embodiment, since a single-phase PWM rectifier is applied to the power conversion device that receives single-phase AC power, the filter circuit and capacitor of the power conversion device can be miniaturized. As a result, the cost of the DC power distribution system can be reduced.

[0069] Implementation method 5.

[0070] In Embodiment 4, a method for suppressing harmonic components in a power conversion device connected to a single-phase AC system was described. In Embodiment 5, a method for suppressing harmonic components in a power conversion device connected to a three-phase AC system was described.

[0071] Figure 7 This is a structural diagram of the power conversion device 41 of the DC power distribution system according to this embodiment. The power conversion device 41 is an AC-DC power conversion device used to receive three-phase AC power from the power system 1 and convert it into DC power. Figure 7As shown, the power conversion device 41 of this embodiment includes an AC input terminal 410 for inputting three-phase AC power from the power system 1, a transformer 411, a filter circuit 412, a rectifier 413, and a DC output terminal 414 for outputting DC power. Furthermore, the structure of the DC power distribution system in this embodiment is the same as that of the DC power distribution system in Embodiment 1.

[0072] Transformer 411 includes a primary winding, a secondary winding, and a tertiary winding. Transformer 411 converts the three-phase AC power input to the primary winding into voltage and outputs it to the secondary winding and tertiary winding respectively.

[0073] In order to prevent harmonics generated by rectifier 413 from flowing into power system 1, filter circuit 412 is connected, and filter circuit 412 is connected as needed.

[0074] The rectifier 413 includes 12 diodes D11 to D22, which are semiconductor elements. Typically, Figure 7 The rectifier 413 shown is also known as a 12-pulse rectifier or simply a diode rectifier. Figure 4 The 6-pulse rectifier shown is a series-connected structure. For example... Figure 7 As shown, the outputs of the secondary and tertiary windings of transformer 411 are respectively input to two 6-pulse rectifiers connected in series.

[0075] Compared to a 6-pulse rectifier, a 12-pulse rectifier outputs fewer harmonics. Therefore, compared to the DC power distribution system of Embodiment 3, the DC power distribution system of this embodiment has fewer harmonics. Therefore, in the DC power distribution system of this embodiment, the filter circuit 412 can be reduced in size or even removed. Furthermore, when the power quality requirements of the three-phase AC system of power system 1 are strict and the allowable harmonics are low, the power conversion device 41 that inputs power to power system 1 needs to use a 12-pulse rectifier.

[0076] Furthermore, in the DC power distribution system of this embodiment, the drooping characteristic of the magnetic coupling between the secondary and tertiary windings of the transformer 411 is utilized to suppress the short-circuit current during a short-circuit fault. Therefore, the tolerance to short-circuit faults is improved. Additionally, by connecting multiple rectifiers 413 in parallel, the current capacity of the power conversion device 41 can be increased; and by connecting multiple diodes D11 to D22 in parallel as needed, the current capacity can also be increased.

[0077] Implementation method 6.

[0078] Figure 8 This is a structural diagram of the power conversion device 41 of the DC power distribution system according to this embodiment. The power conversion device 41 is an AC-DC power conversion device used to receive three-phase AC power from the power system 1 and convert it into DC power. Figure 8 As shown, the power conversion device 41 of this embodiment includes an AC input terminal 410 for inputting three-phase AC power from the power system 1, a transformer 411, a filter circuit 412, a rectifier 413, and a DC output terminal 414 for outputting DC power. Furthermore, in the power conversion device 41 of this embodiment, a capacitor 415 for suppressing output voltage ripple is connected in parallel with the DC output terminal 414. The transformer 411 and the filter circuit 412 are the same as those in the power conversion device 41 of Embodiment 3. Additionally, the structure of the DC power distribution system of this embodiment is the same as that of the DC power distribution system of Embodiment 1.

[0079] The rectifier 413 in this embodiment is obtained by replacing the six diodes D11 to D16 of the rectifier 413 of the power conversion device 41 in embodiment 3 with six semiconductor switching elements Q11 to Q16. Typically, Figure 8 The rectifier 413 shown is referred to as a three-phase PWM rectifier. Semiconductor switching elements Q11 to Q16 can be, for example, IGBTs or MOSFETs with self-arc suppression functions, such as diodes connected in reverse parallel. Multiple elements can be connected in parallel as needed to increase current capacity. Furthermore, the switching operation of semiconductor switching elements Q11 to Q16 is controlled by a control signal sent from a control unit not shown in the figure.

[0080] Since the rectifier 413 in this embodiment is composed of a three-phase PWM rectifier, harmonic components output through the switching operations of semiconductor switching elements Q11 to Q16 can be suppressed, thus enabling the miniaturization of the filter circuit 412. Furthermore, by performing the switching operations of semiconductor switching elements Q21 to Q24 at a higher frequency, the filter circuit 412 can be miniaturized. Additionally, since the ripple of the DC voltage output through the switching operations of semiconductor switching elements Q11 to Q16 can be reduced, the capacitor 415 can be miniaturized.

[0081] Furthermore, given the stringent requirements for power quality in the three-phase AC system of power system 1 and the low permissible harmonics, the power conversion device 41 for the power input to power system 1 needs to employ a three-phase PWM rectifier.

[0082] In the DC power distribution system of this embodiment, since a three-phase PWM rectifier is applied to the power conversion device that receives three-phase AC power, the filter circuit and capacitors of the power conversion device can be miniaturized. As a result, the cost of the DC power distribution system can be reduced. In addition, multiple rectifiers 413 can be connected in parallel to increase the current capacity of the power conversion device 41.

[0083] Implementation method 7.

[0084] In the DC power distribution systems of Embodiments 3 to 6, the AC-DC power conversion device was described. In the DC power distribution system of Embodiment 7, the DC-DC power conversion device was described. Furthermore, the structure of the DC power distribution system in this embodiment is the same as that of the DC power distribution system in Embodiment 1.

[0085] Figure 9 This is a structural diagram of the power conversion device 41 of the DC power distribution system according to this embodiment. This power conversion device 41 is a DC-DC power conversion device that receives DC power from the power system 1 and converts it into DC power with different voltages. Figure 9 As shown, the power conversion device 41 of this embodiment includes a DC input terminal 416 for inputting DC power from the power system 1, a capacitor 417 connected in parallel to the DC input terminal 416, two semiconductor switching elements 418 connected in parallel with the capacitor 417, and a DC output terminal 414 for outputting DC power. Furthermore, the power conversion device 41 includes a DC reactor 419 connected between the midpoint of the two semiconductor switching elements 418 and the DC output terminal, and a capacitor 415 connected in parallel to the DC output terminal 414. Figure 9 The power conversion device 41 shown is also called a bidirectional chopper, which is a power conversion device capable of bidirectionally transmitting power between the DC input terminal 416 and the DC output terminal 414.

[0086] The switching operation of the two semiconductor switching elements 418 is controlled by a control signal sent from a control unit not shown in the figure. By controlling the switching operation of the semiconductor switching elements 418, the power conversion device 41 of this embodiment can precisely control the voltage of the DC power output from the DC output terminal 414 to a constant value, thereby improving the power quality of the DC power distribution system 10. Furthermore, in the event of a short-circuit fault, the short-circuit current is suppressed by the DC reactor 419; therefore, by appropriately designing the reactance value of the DC reactor 419, the short-circuit withstand capability of the power conversion device 41 can be improved. Additionally, by connecting multiple semiconductor switching elements 418 in parallel using a structure where two semiconductor switching elements 418 are connected in series, the current capacity of the power conversion device 41 can be increased.

[0087] Figure 10 This is a structural diagram of another power conversion device 41 in the DC power distribution system of this embodiment. This power conversion device 41 is a DC-DC power conversion device that receives DC power from the power system 1 and converts it into DC power with different voltages.

[0088] like Figure 10As shown, the power conversion device 41 of this embodiment includes a DC input terminal 416 for inputting DC power from the power system 1, a capacitor 417 connected in parallel to the DC input terminal 416, a primary bridge circuit 413a composed of four semiconductor switching elements Q11 to Q14, a transformer 411, a secondary bridge circuit 413b composed of four semiconductor switching elements Q15 to Q18, a DC output terminal 414 for outputting DC power, and a capacitor 415 connected in parallel to the DC output terminal 414. Figure 10 The power conversion device 41 shown is also called a bidirectional isolated DC-DC power conversion device, which is a power conversion device capable of bidirectionally transmitting power between the DC input terminal 416 and the DC output terminal 414.

[0089] The switching operations of semiconductor switching elements Q11 to Q14 in the primary side bridge circuit 413a and semiconductor switching elements Q15 to Q18 in the secondary side bridge circuit 413b are controlled by control signals sent from a control unit not shown in the figure. By controlling the switching operations of semiconductor switching elements Q11 to Q18, the power conversion device 41 of this embodiment can precisely control the voltage of the DC power output from the DC output terminal 414 to a constant value, thereby improving the power quality of the DC power distribution system 10. Furthermore, by performing the switching operations of semiconductor switching elements Q11 to Q18 at a higher frequency, the transformer 411 can be miniaturized. In addition, the transformer 411 has a short-circuit impedance, which can suppress short-circuit current in the event of a short-circuit fault. Furthermore, by setting this short-circuit impedance to an appropriate value, the short-circuit current can be suppressed below the maximum allowable current value of the semiconductor elements. In addition, the current capacity of the power conversion device 41 can be increased by connecting multiple primary-side bridge circuits 413a and secondary-side bridge circuits 413b in parallel, and the current capacity can also be increased by connecting multiple semiconductor switching elements Q11 to Q18 in parallel as needed.

[0090] This application describes various exemplary embodiments, but the various features, forms and functions described in one or more embodiments are not limited to the application of a specific embodiment, and can be applied to the embodiment alone or in various combinations.

[0091] Therefore, it can be assumed that numerous variations not illustrated are also included within the scope of the technology disclosed in this application. For example, this includes cases where at least one constituent element is modified, added to, or omitted, and cases where at least one constituent element is extracted and combined with constituent elements of other embodiments.

[0092] Label Explanation

[0093] 1, 2 Power system; 10 DC power distribution system; 11, 12 First current cut-off section; 21, 22 Second current cut-off section; 31, 32, 33 Third current cut-off section; 41, 42 Power conversion device; 51, 52, 53 DC load; 60 DC bus; 70 Short circuit fault; 71, 72 Short circuit current; 410, 420 AC input terminal; 411, 421 Transformer; 412, 422 Filter circuit; 413, 423 Rectifier; 414, 424 DC output terminal; 417, 415, 425 Capacitor; 413a Primary side bridge circuit; 413b Secondary side bridge circuit; 416 DC input terminal; 418 Semiconductor switching element; 419 DC reactor.

Claims

1. A DC power distribution system, comprising: Multiple power conversion devices that convert power supplied from multiple power systems into DC power and output it; A DC bus through which DC power output from the plurality of said power conversion devices flows; Multiple power distribution lines, each branching off from the DC bus; A plurality of first current cut-off sections are respectively connected between the plurality of said power systems and the plurality of said power conversion devices; A plurality of second current cut-off sections are respectively connected between the plurality of power conversion devices and the DC bus; as well as Multiple third current interruption sections are respectively installed on multiple of the aforementioned power distribution lines. The DC power distribution system is characterized in that... The cutting current value of the plurality of third current cutting sections is set to be smaller than the maximum allowable current value of the power conversion device, which is the value at which the short-circuit current in the plurality of power conversion devices reaches the maximum allowable current value of the power conversion device in the shortest time.

2. The DC power distribution system as described in claim 1, characterized in that, The cutting current value of the second current cutting section is smaller than the maximum allowable current value of the power conversion device connected to the second current cutting section.

3. The DC power distribution system as described in claim 1 or 2, characterized in that, The maximum allowable current values ​​of the multiple power conversion devices are the same.

4. The DC power distribution system as described in any one of claims 1 to 3, characterized in that, The harmonics output from the plurality of power conversion devices are within the permissible range of harmonics specified by the power system that supplies the power to the power conversion devices.

5. The DC power distribution system as described in any one of claims 1 to 4, characterized in that, At least one of the power conversion devices is an AC-DC power conversion device comprising an AC input terminal, a transformer connected to the AC input terminal, a filter circuit connected to the output side of the transformer, a diode rectifier connected to the filter circuit, and a DC output terminal connected to the output side of the diode rectifier.

6. The DC power distribution system as described in any one of claims 1 to 4, characterized in that, At least one of the power conversion devices is an AC-DC power conversion device comprising an AC input terminal, a transformer connected to the AC input terminal, a filter circuit connected to the output side of the transformer, a PWM rectifier connected to the filter circuit, and a DC output terminal connected to the output side of the PWM rectifier.

7. The DC power distribution system as described in any one of claims 1 to 4, characterized in that, At least one of the power conversion devices is a DC-DC power conversion device comprising a DC input terminal, a first capacitor connected in parallel with the DC input terminal, two semiconductor switching elements connected in parallel with the first capacitor, a DC output terminal connected to the midpoint of the two semiconductor switching elements, a DC reactor connected between the midpoint of the two semiconductor switching elements and the DC output terminal, and a second capacitor connected in parallel with the DC output terminal.

8. The DC power distribution system as described in any one of claims 1 to 4, characterized in that, At least one of the power conversion devices is a DC-DC power conversion device comprising a DC input terminal, a first capacitor connected in parallel with the DC input terminal, a primary bridge circuit connected in parallel with the first capacitor, a DC output terminal, a second capacitor connected in parallel with the DC output terminal, a secondary bridge circuit connected in parallel with the second capacitor, and a transformer connected between the primary bridge circuit and the secondary bridge circuit.

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