DC circuit breaker and method for controlling DC circuit breaker

Abstract

To provide a DC circuit breaker that makes it possible to confirm whether a secondary circuit of the DC circuit breaker does not have short-circuits in advance before a semiconductor switch is turned ON.SOLUTION: A DC circuit breaker (10) has a first switch (SW1) and a second switch (SW2), connected to input terminals (I1, I2), closed to charge a capacitor (C), and also has a third switch (SW3) closed with the first switch and second switch open to measure the potential difference between output terminals (O1, O2) with electric charges of the capacitor, and when the potential difference is equal to or larger than a predetermined potential difference, the first switch and second switch are closed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a DC circuit breaker. [Background technology]

[0002] DC power distribution networks that supply DC power to various electric loads have been proposed. DC power distribution networks are required to supply DC power to electric loads with high reliability and high quality. Therefore, in such DC power distribution networks, it is common to provide a DC circuit breaker between a DC power source and an electric load in order to protect the system from an overcurrent when a short circuit or the like occurs in the electric load.

[0003] Patent Document 1 discloses a technique in which a threshold value for determining an overcurrent is changed with the passage of time after conduction so that an inrush current is not detected as an overcurrent even if an inrush current is detected.

[0004] For DC circuit breakers, semiconductor switches are preferred over mechanical contacts. This is because mechanical circuit breakers use conductors to make contact and open the contacts to break the current, so there is a limit to the number of times they can be opened and closed when current is flowing due to wear on the contacts. On the other hand, semiconductor circuit breakers use semiconductor switches to open and close the current, allowing for fast and reliable interruption. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-172603 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned semiconductor switch has a smaller rated current than mechanical contacts and is vulnerable to large currents such as short circuit current or inrush current, which can cause damage. As a countermeasure against inrush current, when connecting the primary circuit and secondary circuit in a DC circuit breaker, the connection is first made with mechanical contacts, and then switched to the semiconductor switch over time. Therefore, inrush current does not flow through the semiconductor switch.

[0007] In the event of a short circuit, a large current different from the inrush current flows even at the timing when the semiconductor switch is switched on, so the semiconductor switch must be able to handle the large current. This large current is often larger than the rated current of the semiconductor switch, and can cause the semiconductor switch to be damaged.

[0008] Therefore, an object of one aspect of the present invention is to provide a DC circuit breaker that can check in advance whether there is a short circuit in the secondary circuit of the DC circuit breaker before turning on a semiconductor switch. [Means for solving the problem]

[0009] In order to solve the above problems, a DC circuit breaker according to one embodiment of the present invention comprises a first input terminal and a second input terminal to which a DC power source is connected, a first output terminal and a second output terminal to which a DC load is connected, a connection point located between the first input terminal and the first output terminal, a switch unit connected between the first output terminal and the connection point, a capacitor and a resistor connected in series with each other and connected between the connection point and the second output terminal, a primary side switch including at least one of a first switch connected between the first input terminal and the connection point and a second switch connected between the second input terminal and the second output terminal, and a voltmeter that measures a potential difference between the first output terminal and the second output terminal, and when the switch unit is off, the primary side switch is turned on to charge the capacitor, and when the primary side switch is off, the switch unit is turned on to measure the potential difference, and the primary side switch is turned on based on the potential difference. Effect of the Invention

[0010] According to one aspect of the present invention, it is possible to check in advance whether or not there is a short circuit in the secondary circuit of the DC circuit breaker before turning on a semiconductor switch in the DC circuit breaker. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a circuit diagram showing a configuration of a DC circuit. [Diagram 2] 4 is a flowchart showing the operation of a DC circuit breaker. [Diagram 3] 4 is a timing chart of each part of the DC circuit breaker. [Figure 4] FIG. 11 is a circuit diagram showing the state of a DC circuit as a result of the processes in S11 and S12. [Diagram 5] FIG. 11 is a circuit diagram showing the state of a DC circuit as a result of the process in S14. [Figure 6] FIG. 2 is a circuit diagram showing a configuration of a DC circuit breaker in a reference example. [Figure 7] 4 is a timing chart showing the operation of a DC circuit breaker in a reference example. [Figure 8] 11 is a timing chart showing another operation of the DC circuit breaker in the reference example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Embodiment 1] Hereinafter, one embodiment of the present invention will be described in detail.

[0013] (Configuration of DC circuit 1) 1 is a circuit diagram showing the configuration of a DC circuit 1. The DC circuit 1 includes a DC breaker 10, a DC power source PW, and a DC load LD.

[0014] The DC circuit breaker 10 is an electrical device that conducts electricity from a DC power source PW, which is a primary circuit connected to a first input terminal I1 and a second input terminal I2, to a DC load LD, which is a secondary circuit connected to a first output terminal O1 and a second output terminal O2.

[0015] In addition, the DC circuit breaker 10 judges the state of the DC load LD, and when it detects a current equal to or greater than the rated current of the DC circuit breaker 10, it operates to cut off the electricity in the primary circuit without conducting it to the secondary circuit.

[0016] The DC power supply PW outputs a DC power supply voltage E between the first input terminal I1 and the second input terminal I2. The DC load LD consumes DC power supplied from the first output terminal O1 and the second output terminal O2.

[0017] (Configuration of DC circuit breaker 10) The DC circuit breaker 10 includes a first switch SW1, a second switch SW2, a third switch SW3, a semiconductor switch TR, a snubber circuit SN, a capacitor C, a resistor R, a voltmeter V, an ammeter A, and a control unit CN.

[0018] The DC circuit breaker 10 has a first input terminal I1 and a second input terminal I2 as input terminals, and is connected to the primary circuit. The DC circuit breaker 10 also has a first output terminal O1 and a second output terminal O2 as output terminals, and is connected to the secondary circuit.

[0019] An ammeter A is connected to the first input terminal I1, and measures the current input from the first input terminal I1. The ammeter A is also connected to the primary side of the first switch SW1, and a connection point (node) of the secondary side of the first switch SW1 is referred to as a connection point J. That is, the connection point J is located between the first input terminal and the first output terminal. The second switch SW2 is connected between the second input terminal I2 and the second output terminal O2. The first switch SW1 and the second switch SW2 are relays or electromagnetic contactors having mechanical contacts. Here, the ammeter A has been described as being connected to the first input terminal I1, but is not limited to this configuration and may be connected to the second input terminal I2. At least one of the first switch SW1 and the second switch SW2 is referred to as a primary side switch.

[0020] Between the connection point J and the first output terminal O1, the third switch SW3, the snubber circuit SN, the semiconductor switch TR, and the diode D are connected in parallel with each other. The third switch SW3 is a relay or an electromagnetic contactor having a mechanical contact. The snubber circuit SN is a snubber circuit composed of a capacitor and a resistor, and has the effect of suppressing a transient response. The snubber circuit SN is not limited to the above configuration, and may be any circuit as long as it has the function of a snubber circuit. The semiconductor switch TR is a switching element such as a transistor, a FET (Field Effect Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and an IGBT (Insulated Gate Bipolar Transistor). The diode D is connected to protect the semiconductor switch TR. The semiconductor switch TR and the third switch SW3 are collectively referred to as a switch unit. In other words, the switch unit is connected between the first output terminal and the connection point.

[0021] The capacitor C and the resistor R are connected in series between the connection point J and the second output terminal O2. The capacitor C and the resistor R function as a surge protection circuit between the first input terminal I1 and the second input terminal I2.

[0022] The potential difference Vout between the first output terminal O1 and the second output terminal O2 is measured by a voltmeter V, and the voltmeter V outputs the potential difference Vout to the control unit CN. Also, the current Iin measured by the ammeter A is output to the control unit CN. The control unit CN controls the first switch SW1, the second switch SW2, the third switch SW3, and the semiconductor switch TR based on the potential difference Vout and the current Iin.

[0023] (Operation of DC circuit breaker 10) Fig. 2 is a flowchart showing the operation of the DC circuit breaker 10. Fig. 3 is a timing chart of each part of the DC circuit breaker 10. Hereinafter, a case where the DC circuit breaker 10, which has cut off the primary circuit and the secondary circuit, brings the primary circuit and the secondary circuit into conduction will be described. In particular, a process of checking for a short circuit in the secondary circuit when the DC circuit breaker 10 brings the primary circuit and the secondary circuit into conduction will be described.

[0024] In S11, the control unit CN closes (ON) the first switch SW1 in response to a conduction command from a user operation or an automatic closing machine for the DC circuit breaker 10. In addition, in S12, the control unit CN closes the second switch SW2. S11 and S12 do not have to be processed in order, and may be processed simultaneously. At this time, the third switch SW3 is open (OFF), and the semiconductor switch TR is OFF.

[0025] Fig. 4 is a circuit diagram showing the state of the DC circuit 1 as a result of the processes of S11 and S12. As shown by the dotted arrow in Fig. 4, a closed circuit is formed by the DC power supply PW, the first switch SW1, the capacitor C, the resistor R, and the second switch SW2. Therefore, the capacitor C is charged by the DC power supply PW (charging step).

[0026] In S13, the control unit CN charges the capacitor C until time t13. After that, the control unit CN opens the first switch SW1 and the second switch SW2. As a result, the charge stored in the capacitor C is held in the capacitor C.

[0027] In S14, the control unit CN closes the third switch SW3 at time t14. Fig. 5 is a circuit diagram showing the state of the DC circuit 1 as a result of the processing of S14. As shown by the dotted arrow in Fig. 5, the charge stored in the capacitor C flows through the third switch SW3 to the DC load LD and is consumed.

[0028] In S15, at time t15, which is tdelay after time t14, the control unit CN measures the potential difference Vout using the voltmeter V (measurement step). If the potential difference Vout is equal to or smaller than the predetermined threshold Vset (No in S15), the process proceeds to S16. On the other hand, if the potential difference Vout is greater than the predetermined threshold Vset (Yes in S15), the process proceeds to S17.

[0029] In S16, since the potential difference Vout is equal to or less than the predetermined threshold value Vset, the control unit CN considers the possibility that the secondary circuit is short-circuited, and cuts off the DC power by the DC circuit breaker 10. That is, the control unit CN opens the third switch SW3. At this time, the control unit CN may notify an external device or administrator of the short-circuit of the secondary circuit by using a display or communication. In addition, the first switch SW1 and the second switch SW2 are also kept open.

[0030] In S17, the control unit CN determines that the secondary circuit is not short-circuited because the potential difference Vout is greater than the predetermined threshold value Vset. Therefore, the control unit CN causes the DC power to be conducted from the primary circuit to the secondary circuit by the DC circuit breaker 10. That is, the control unit CN closes the first switch SW1 and the second switch SW2 (opening and closing step). Since the DC power source PW is connected, the DC load LD obtains sufficient power, and an inrush current instantaneously flows through the third switch SW3.

[0031] In S18, the control unit CN turns on the semiconductor switch TR at time t18 when a sufficient time has elapsed for the inrush current to subside. In S19, the control unit CN opens the third switch SW3 at time t19 after time t18. After this, DC power is supplied from the primary circuit to the secondary circuit via the semiconductor switch TR.

[0032] The purpose of switching the connection from the third switch SW3 to the semiconductor switch TR is to ensure responsiveness to an overcurrent. That is, since the response speed of the third switch SW3 is several milliseconds and the response speed of the semiconductor switch TR is several microseconds, the semiconductor switch TR can interrupt an overcurrent that exceeds the rated current of the DC circuit breaker 10 more quickly. However, the rated current of the semiconductor switch TR is generally smaller than that of the third switch SW3, and there is a risk of it being damaged by the flow of a large current such as an inrush current. Therefore, in the DC circuit breaker, immediately after closing when there is a high possibility of a large current flowing due to an inrush current, the third switch SW3 connects the primary circuit to the secondary circuit.

[0033] (Description of DC circuit breaker 100 in reference example) Here, the DC circuit breaker 100 of the reference example will be described.

[0034] 6 is a circuit diagram showing a configuration of a DC circuit breaker 100 in a reference example. The DC circuit breaker 100 in the reference example does not have a capacitor C, a resistor R, and a voltmeter V, as compared with the DC circuit breaker 10 in the first embodiment.

[0035] Therefore, the only means for detecting a short circuit in the secondary circuit is the current Iin detected by ammeter A.

[0036] Hereinafter, a case will be described in which the primary circuit and the secondary circuit are made conductive by the DC circuit breaker 100, which has interrupted the primary circuit and the secondary circuit. In particular, please compare the operation of the DC circuit breaker 10 and the DC circuit breaker 100 when a short circuit occurs in the secondary circuit.

[0037] 7 is a timing chart showing the operation of the DC circuit breaker 100 in the reference example. In the DC circuit breaker 100, after the first switch SW1 and the second switch SW2 are closed, the third switch SW3 is closed (time t21). As a result, if the secondary circuit is short-circuited, a short-circuit current flows from the primary circuit to the secondary circuit, which is a large current. Therefore, the ammeter A detects that a current equal to or greater than a predetermined current is flowing, and the DC circuit breaker 100 cuts off the connection between the primary circuit and the secondary circuit (time t22). The first switch SW1 and the second switch SW2 may be opened simultaneously with time t22.

[0038] FIG. 8 is a timing chart showing another operation of the DC circuit breaker 100 in the reference example. In FIG. 8, the timing at which the DC circuit breaker 100 cuts off the connection from the primary circuit to the secondary circuit is later than that in FIG. 7. After the first switch SW1 and the second switch SW2 are closed, the third switch SW3 is closed (time t21), and then the semiconductor switch TR is turned on in addition to the third switch SW3 (time t32). After that, the third switch SW3 is closed (time t33), and then the semiconductor switch TR is turned off (time t34). Therefore, a large current exceeding the rated current due to the short circuit current flows through the semiconductor switch TR, which leads to damage to the semiconductor switch TR. The first switch SW1 and the second switch SW2 may be opened at the same time as time t34.

[0039] (Effects of DC circuit breaker 10) In the DC circuit breaker 10, when an operation for conducting the primary circuit and the secondary circuit is performed, the capacitor C is first charged. Then, a closed circuit between the capacitor C and the DC load LD is formed by a switch unit using the third switch SW3 or the semiconductor switch TR, and the potential difference Vout is measured with the charged charge. When the potential difference Vout satisfies a predetermined condition, it is possible to check whether or not the DC load LD is short-circuited. Therefore, before connecting DC power from the primary circuit to the secondary circuit, it is possible to check whether or not the secondary circuit is short-circuited, and safety can be ensured. The predetermined condition is when the potential difference is equal to or greater than a predetermined threshold value.

[0040] After the third switch SW3 checks the continuity of the switch unit, the third switch SW3 passes a large current due to an inrush current that occurs when the first switch SW1 and the second switch SW2 are closed to connect the primary circuit to the secondary circuit. After the inrush current passes, the semiconductor switch TR is turned on and the third switch SW3 is opened, so that the semiconductor switch TR can quickly cut off the connection from the primary circuit to the secondary circuit without applying a momentary large current to the semiconductor switch TR. This makes it possible to realize a DC circuit breaker 10 that achieves both a long life of the semiconductor switch TR and a high-speed response by the semiconductor switch TR. Therefore, by detecting a short circuit before the primary circuit is connected to the secondary circuit, damage and a decrease in reliability of the semiconductor switch TR are suppressed, and failure prevention and a long life of the DC circuit breaker 10 are realized.

[0041] In addition, the snubber circuit connected in parallel to the switch section can absorb the transient large current and voltage that accompanies large currents such as inrush current. Furthermore, the capacitor C and resistor R can also function as a snubber circuit for large currents and large voltages in the DC circuit 1.

[0042] (Normal operation of DC circuit breaker 10) When the current Iin measured by the ammeter A becomes equal to or greater than a predetermined current, the control unit CN can shut off the DC circuit breaker 10, i.e., turn off the semiconductor switch TR. At this time, the control unit CN may simultaneously open the first switch SW1, the second switch SW2 (and the third switch SW3) in addition to the semiconductor switch TR.

[0043] By the above-described operation, during normal operation except when DC circuit breaker 10 starts to connect the primary circuit and secondary circuit, if a current equal to or greater than the rated current of DC circuit breaker 10 is detected, the DC circuit breaker can cut off the connection between the primary circuit and secondary circuit.

[0044] (Modification) Either the first switch SW1 or the second switch SW2 may be omitted in the DC circuit breaker 10. In this case, the number of components of the DC circuit breaker 10 can be reduced, and therefore the cost of the DC circuit breaker 10 can be reduced.

[0045] In addition, since the first switch SW1 and the second switch SW2 are relays or electromagnetic contactors having mechanical contacts, there is a limit to the number of times they can be opened and closed. This also has the advantage that the reliability of the components inside the DC circuit breaker 10 can be easily ensured.

[0046] [Software implementation example] The functions of DC circuit breakers 10, 10a, 10b (hereinafter referred to as the "device") can be realized by a program for causing a computer to function as the device, and a program for causing a computer to function as each control block (particularly the control unit CN) of the device.

[0047] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program to realize each function described in each of the above embodiments.

[0048] The program may be non-transitory and may be recorded in one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be provided to the device via any wired or wireless transmission medium.

[0049] In addition, some or all of the functions of each of the control blocks can be realized by a logic circuit. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention. In addition, the functions of each of the control blocks can be realized by, for example, a quantum computer.

[0050] 〔summary〕 In order to solve the above problems, a DC circuit breaker according to one embodiment of the present invention includes a first input terminal and a second input terminal to which a DC power supply is connected, a first output terminal and a second output terminal to which a DC load is connected, a connection point located between the first input terminal and the first output terminal, a switch unit connected between the first output terminal and the connection point, a capacitor and a resistor connected in series with each other and connected between the connection point and the second output terminal, a primary side switch including at least one of a first switch connected between the first input terminal and the connection point and a second switch connected between the second input terminal and the second output terminal, and a voltmeter that measures a potential difference between the first output terminal and the second output terminal, and when the switch unit is off (shutdown state), the capacitor is charged by turning on the primary side switch, and when the primary side switch is off, the switch unit is turned on (conducting state) to measure the potential difference, and the primary side switch is turned on based on the potential difference.

[0051] According to the above configuration, in the DC circuit breaker, it is possible to check whether or not a short circuit has occurred between the first output terminal and the second output terminal before turning on the switch unit.

[0052] In the DC circuit breaker according to the second aspect of the present invention, the primary side switch may be turned on when the potential difference is equal to or greater than a predetermined potential difference.

[0053] According to the above configuration, when there is no short circuit between the output terminals, the output terminal can be safely brought into electrical continuity with the input terminal by turning on the primary side switch.

[0054] The DC circuit breaker according to a third aspect of the present invention may be configured to turn off the primary side switch and the switch unit when the potential difference is less than a predetermined potential difference.

[0055] According to the above configuration, when a short circuit occurs between the output terminals, safety can be ensured by turning off the primary side switch and the switch unit, thereby preventing electrical continuity between the output terminal and the input terminal.

[0056] In the DC circuit breaker according to a fourth aspect of the present invention, the switch section may include a semiconductor switch and a third switch connected in parallel.

[0057] According to the above configuration, the switch section can be configured by the semiconductor switch and the third switch.

[0058] The DC circuit breaker of aspect 5 of the present invention may measure the potential difference by turning on the third circuit breaker while keeping the primary side circuit breaker off, and if the potential difference is equal to or greater than a predetermined potential difference, turn on all of the first circuit breaker and / or the second circuit breaker, turn on the semiconductor switch, and then turn off the third circuit breaker.

[0059] According to the above configuration, when the DC circuit breaker is turned on, the inrush current flows through the third switch, and after the current stabilizes, the semiconductor switch capable of high-speed response is switched over to. Therefore, it is possible to avoid regular operation with the third switch, which has a lower response and durability than the semiconductor switch.

[0060] The DC breaker according to a sixth aspect of the present invention may further include a snubber circuit connected in parallel to the switch unit.

[0061] According to the above configuration, it is possible to suppress the transient response that occurs when the switch section is turned on.

[0062] The DC circuit breaker according to a seventh aspect of the present invention may further include an ammeter that measures a current flowing through the primary side switch.

[0063] According to the above configuration, not only when the switch unit is turned on, but also during normal operation, an overcurrent can be detected by measuring the current and the DC power can be cut off by the DC breaker.

[0064] In another aspect of the present invention, a control method for a DC circuit breaker includes a first input terminal and a second input terminal to which a DC power source is connected, a first output terminal and a second output terminal to which a DC load is connected, a connection point located between the first input terminal and the first output terminal, a switch unit connected between the first output terminal and the connection point, and a primary side switch including at least one of a first switch connected between the first input terminal and the connection point, and a second switch connected between the second input terminal and the second output terminal, wherein the DC circuit breaker further includes a voltmeter that measures a potential difference between the first output terminal and the second output terminal, and a capacitor and a resistor that are connected in series with each other and are connected between the connection point and the second output terminal, and the control method includes a charging step of charging the capacitor by turning on the primary side switch while the switch unit is off, a measuring step of turning on the switch unit while the primary side switch is off and measuring the potential difference, and a switching step of turning on the primary side switch based on the potential difference.

[0065] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0066] 1 DC circuit 10,100 DC circuit breaker A Ammeter C Capacitor I1 First input terminal I2 Second input terminal Iin current O1 First output terminal O2 2nd output terminal R resistance SN Snubber circuit SW1 First switch (primary side switch) SW2 Second switch (primary side switch) SW3 Third switch (switch section) TR semiconductor switch (switch section) V Voltmeter Vout Potential difference Vset threshold

Claims

1. a first input terminal and a second input terminal to which a DC power source is connected; a first output terminal and a second output terminal to which a DC load is connected; a connection point located between the first input terminal and the first output terminal; a switch section connected between the first output terminal and the connection point; a capacitor and a resistor connected in series between the connection point and the second output terminal; a primary side switch including at least one of a first switch connected between the first input terminal and the connection point and a second switch connected between the second input terminal and the second output terminal; a voltmeter that measures a potential difference between the first output terminal and the second output terminal, The capacitor is charged by turning on the primary side switch while the switch unit is in an off state. With the primary side switch turned off, the switch unit is turned on to measure the potential difference; A DC circuit breaker that turns on the primary side switch based on the potential difference.

2. 2. The DC circuit breaker according to claim 1, wherein the primary side switch is turned on when the potential difference is equal to or greater than a predetermined potential difference.

3. 3. The DC circuit breaker according to claim 1, wherein the primary side switch and the switch unit are turned off when the potential difference is less than a predetermined potential difference.

4. 4. The DC circuit breaker according to claim 1, wherein the switch section comprises a semiconductor switch and a third switch connected in parallel.

5. With the primary side switch in an off state, the third switch is turned on to measure the potential difference; When the potential difference is equal to or greater than a predetermined potential difference, the primary side switch is turned on; 5. The DC circuit breaker according to claim 4, wherein the third switch is turned off after the semiconductor switch is turned on.

6. The DC circuit breaker according to claim 1 , further comprising a snubber circuit connected in parallel to the switch unit.

7. The DC circuit breaker according to claim 1 , further comprising an ammeter that measures a current flowing through the primary side switch.

8. a first input terminal and a second input terminal to which a DC power source is connected; a first output terminal and a second output terminal to which a DC load is connected; a connection point located between the first input terminal and the first output terminal; a switch section connected between the first output terminal and the connection point; A method for controlling a DC circuit breaker including a primary side switch including at least one of a first switch connected between the first input terminal and the connection point, and a second switch connected between the second input terminal and the second output terminal, The DC circuit breaker comprises: a voltmeter that measures a potential difference between the first output terminal and the second output terminal; a capacitor and a resistor connected in series between the connection point and the second output terminal; a charging step of charging the capacitor by turning on the primary side switch while the switch unit is in an off state; a measuring step of measuring the potential difference by turning on the switch unit while the primary side switch is turned off; and a switching step of turning on the primary side switch based on the potential difference.

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