DC circuit breakers and DC power transmission systems

Abstract

In a DC power transmission system, loads located downstream of a DC circuit breaker are protected more reliably by the DC circuit breaker than in conventional systems. [Solution] A DC circuit breaker (1) located upstream of a load (LD) in a DC power transmission system (100) is connected to a DC power transmission line (81) in the DC power transmission system (100) and comprises a semiconductor switch (SW) having a gate terminal (GT), a current sensor (11) that detects the current value of the current flowing through the semiconductor switch (SW) and the rate of change of the current value over time, and a control unit (20) that controls the semiconductor switch (SW) by supplying a gate voltage to the gate terminal (GT). The control unit (20) reduces the current flowing through the semiconductor switch (SW) when the semiconductor switch (SW) is in a conductive state by changing the gate voltage based on the rate of change of the current detected by the current sensor (11).

Description

[Technical Field]

[0001] The following disclosure relates to DC circuit breakers. [Background technology]

[0002] Various technologies have been proposed for semiconductor circuit breakers as DC circuit breakers. For example, Patent Document 1 below shows various configuration examples for semiconductor circuit breakers installed in DC power transmission systems. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-251907 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] An object of one aspect of this disclosure is to provide a DC power transmission system in which loads located downstream of a DC circuit breaker are protected more reliably by the DC circuit breaker than in conventional systems. [Means for solving the problem]

[0005] A DC circuit breaker according to one aspect of the present disclosure is a DC circuit breaker positioned upstream of a load in a DC power transmission system, and comprises a semiconductor switch connected to a DC power transmission line in the DC power transmission system and having a gate terminal, and a current sensor that detects the current value of the current flowing through the semiconductor switch and the rate of change of the current value over time, The system includes a control unit that controls the semiconductor switch by supplying a gate voltage to the gate terminal, wherein the control unit reduces the current flowing through the semiconductor switch when the semiconductor switch is in a conductive state by changing the gate voltage based on the rate of change of current detected by the current sensor. [Effects of the Invention]

[0006] According to one aspect of this disclosure, in a DC power transmission system, loads located downstream of a DC circuit breaker can be protected more reliably by the DC circuit breaker than in the conventional method. [Brief explanation of the drawing]

[0007] [Figure 1] This shows an example configuration of a DC power transmission system in Embodiment 1. [Figure 2] This is a diagram illustrating the first gate voltage and the second gate voltage. [Figure 3] This shows an example configuration of a DC power transmission system in Embodiment 2. [Figure 4] This is a flowchart illustrating the processing flow in Embodiment 2. [Figure 5] An example of a time chart for each signal value in Embodiment 2 is shown. [Figure 6] Another example of a time chart for each signal value in Embodiment 2 is shown. [Modes for carrying out the invention]

[0008] [Embodiment 1] Embodiment 1 is described below. For the sake of clarity, components having the same function as those described in Embodiment 1 will be denoted by the same reference numerals in subsequent embodiments, and their descriptions will not be repeated. For the sake of simplicity, explanations of known technical matters will be omitted as appropriate.

[0009] In this specification, each component and each numerical value is merely illustrative, unless otherwise consistent with the content. Therefore, unless otherwise consistent with the content, the positional and connection relationships of each component, for example, are not limited to the examples in each figure.

[0010] (DC circuit breaker 1 and its surrounding components) Figure 1 shows an example configuration of a DC power transmission system 100 in Embodiment 1. The DC power transmission system 100 in the example in Figure 1 comprises a DC circuit breaker 1, a DC power supply DP, and a load LD. In the example in Figure 1, the DC circuit breaker 1 can be positioned downstream of the DC power supply DP and upstream of the load LD. Therefore, in the example in Figure 1, the load LD is located downstream of the DC circuit breaker 1.

[0011] As described below, the DC circuit breaker 1 is equipped with a semiconductor switch SW. As can be understood from this, the DC circuit breaker 1 is an example of a semiconductor circuit breaker. The DC power transmission system 100 is designed to supply power from the DC power source DP to the load LD via the DC circuit breaker 1. The DC circuit breaker 1 selectively interrupts the current (more specifically, the DC current) flowing from the DC power source DP to the load LD.

[0012] In the example shown in Figure 1, the DC circuit breaker 1 is connected to the DC transmission line 81 in the DC power transmission system 100. The DC transmission line 81 includes a positive electrode wire 82p and a negative electrode wire 82n. Therefore, the DC circuit breaker 1 in the example shown in Figure 1 has terminals Tpi and Tni on the upstream side (also referred to as the input side of the DC circuit breaker 1). Terminal Tpi is the positive electrode terminal on the input side of the DC circuit breaker 1, and terminal Tni is the negative electrode terminal on the input side of the DC circuit breaker 1.

[0013] Terminals Tpi and Tni are connected to the DC power supply DP. Specifically, terminal Tpi and the positive terminal of the DC power supply DP are connected by positive wire 82p. On the other hand, terminal Tni and the negative terminal of the DC power supply DP are connected by negative wire 82n.

[0014] In the example shown in Figure 1, the DC circuit breaker 1 has terminals Tpo and Tno on its downstream side (also referred to as the output side of the DC circuit breaker 1). Terminal Tpo is the positive terminal on the output side of the DC circuit breaker 1, and terminal Tno is the negative terminal on the output side of the DC circuit breaker 1.

[0015] Terminal To and terminal Tno are connected to the load LD. Specifically, terminal Tpo and the positive electrode of load LD are connected by the positive electrode line 82p. On the other hand, terminal Tno and the negative electrode of load LD are connected by the negative electrode line 82n.

[0016] In the example of FIG. 1, the DC breaker 1 includes a semiconductor switch SW, a current sensor 11, and a control unit 20. Both the current sensor 11 and the semiconductor switch SW are connected to the DC power transmission line 81. In the example of FIG. 1, the current sensor 11 and the semiconductor switch SW are connected in series on the positive electrode line 82p. In the example of FIG. 1, the current sensor 11 is located upstream with respect to the semiconductor switch SW. In this specification, the current detected by the current sensor 11 is denoted as I in I in may also be referred to as the input current.

[0017] I in the example of FIG. 1 in is the current flowing from the DC power supply DP to the terminal Tpi. I in can be reinterpreted as the current flowing from the DC power supply DP to the load LD. I in is also the current flowing through the semiconductor switch SW. Thus, the current sensor 11 in Embodiment 1 is arranged so as to detect the current flowing through the main semiconductor switch SW.

[0018] As described above, the current sensor 11 in Embodiment 1 detects the current value of the current flowing through the semiconductor switch DW (that is, the value of I in ). In addition, the current sensor 11 in Embodiment 1 also detects the time change rate of I in . In this specification, the time change rate of I in is referred to as the current change rate. The time change rate of I in is typically expressed as dI in / dt. By controlling the semiconductor switch SW in consideration of dI in / dt, more diverse control of the semiconductor switch SW becomes possible. The type of the current sensor 11 is I in and dI inIt is not particularly limited as long as / dt can be detected.

[0019] The semiconductor switch SW in Embodiment 1 only needs to have a gate terminal GT. Embodiment 1 exemplifies the case where the semiconductor switch SW is an FET (Field Effect Transistor).

[0020] However, as will be obvious to those skilled in the art, power semiconductor devices other than FETs can also be used as semiconductor switches. For example, any type of IGBT (Insulated Gate Bipolar Transistor) can be used as a semiconductor switch.

[0021] The conduction state and non-conduction state (offset state) of a semiconductor switch SW are switched according to the gate voltage supplied to the gate terminal GT. Therefore, by supplying a predetermined gate voltage to the gate terminal GT, the semiconductor switch SW can be switched to I in It is possible to selectively block certain signals.

[0022] The control unit 20 controls each part of the DC circuit breaker 1. Therefore, in the example in Figure 1, the control unit 20 has a switching control unit 21. The switching control unit 21 controls the semiconductor switch SW by supplying a predetermined gate voltage to the gate terminal GT. Specifically, the switching control unit 21 controls the conduction state of the semiconductor switch SW by supplying a gate voltage to the gate terminal GT.

[0023] In Embodiment 1, the switching control unit 21 generates a gate voltage to be supplied to the gate terminal GT according to the detection result of the current sensor 11. Then, the switching control unit 21 supplies the generated gate voltage to the gate terminal GT.

[0024] In Embodiment 1, the semiconductor switch SW is assumed to be in a conductive state during the normal operation of the DC circuit breaker 1. Therefore, the switching control unit 21 supplies a first gate voltage to the gate terminal GT during the normal operation of the DC circuit breaker 1. The value of the first gate voltage should be set to correspond to the conductive state of the semiconductor switch SW. However, the value of the first gate voltage should be set to be greater than the value of the second gate voltage, which will be described later. As described above, the semiconductor switch SW can be made conductive by supplying a first gate voltage from the switching control unit 21 to the gate terminal GT.

[0025] In Embodiment 1, the control unit 20 receives I from the current sensor 11. in Based on this, the conductor switch SW is controlled. Therefore, the control unit 20 in the example of Figure 1 has a current value comparison unit 22. The current value comparison unit 22 is I in This is compared to the current threshold (a threshold value for current). In this specification, the current threshold is denoted as th1.

[0026] Specifically, the current value comparison unit 22 is I in It is determined whether or not th1 is greater than or equal to th1. That is, the current value comparison unit 22 uses the following equation (1), I in ≥th1 …(1) Determine whether the condition is met.

[0027] The current value comparison unit 22 is I in If it is determined that th is 1 or greater, that is, if it is determined that equation (1) is satisfied, information indicating that fact is supplied to the switching control unit 21.

[0028] The switching control unit 21 is I inWhen information indicating that is th1 or higher is obtained from the current value comparison unit 22, a cutoff gate voltage is generated as the gate voltage. The value of the cutoff gate voltage should be set to correspond to the cutoff state of the semiconductor switch SW. Therefore, in Embodiment 1, the value of the cutoff gate voltage is set to be smaller than the value of the first gate voltage and smaller than the value of the second gate voltage. Typically, the cutoff gate voltage is set to a value lower than 0V (see, for example, reference numeral 630 in Figure 6 shown below). In this specification, the cutoff gate voltage is denoted as Vg0.

[0029] As described above, by supplying Vg0 from the switching control unit 21 to the gate terminal GT, the semiconductor switch SW can be switched from a conductive state to a disconnected state. This allows the current flowing from the DC power supply DP to the load LD to be interrupted.

[0030] In addition, the control unit 20 in Embodiment 1 receives dI from the current sensor 11. in The semiconductor switch SW is configured to be controlled based on / dt. Therefore, for example, as described below, the control unit 20 sets the gate voltage supplied to the gate terminal GT to dI in It can be changed based on / dt. More specifically, the control unit 20 changes the gate voltage to dI in By changing based on / dt, the conduction state of the semiconductor switch SW is changed. in It can reduce [the problem].

[0031] In the example shown in Figure 1, the control unit 20 has a current change rate comparison unit 23. The current change rate comparison unit 23 is dI in Compare / dt with the current rate of change threshold (a threshold for the rate of change of current). In this specification, the current rate of change threshold is denoted as th2.

[0032] Specifically, the current change rate comparison unit 23 is dI in It is determined whether / dt is greater than or equal to th2. That is, the current change rate comparison unit 23 uses the following equation (2), dI in / dt≧th2 …(2) Determine whether the condition is met.

[0033] The current change rate comparison unit 23 is dI in If it is determined that / dt is th2 or greater, that is, if it is determined that equation (2) is satisfied, information indicating that fact is supplied to the switching control unit 21.

[0034] The switching control unit 21 controls dI in When the current rate of change comparison unit 23 receives information indicating that / dt is th2 or higher, the gate voltage supplied to the gate terminal GT is switched from the first gate voltage to the second gate voltage. The value of the second gate voltage is set to correspond to the conduction state of the semiconductor switch SW. The value of the second gate voltage is set to be smaller than the value of the first gate voltage.

[0035] More specifically, the value of the second gate voltage is set so that the semiconductor switch SW can operate in the active region. The value of the second gate voltage may be determined by the designer of the DC circuit breaker 1, for example, based on the specifications of the semiconductor switch SW.

[0036] (Explanation of the first gate voltage and the second gate voltage) Figure 2 is a diagram illustrating the first and second gate voltages in Embodiment 1. In the example in Figure 2, the first gate voltage is denoted as Vg1 and the second gate voltage is denoted as Vg2. In the example in Figure 2, Vg1 = 20V and Vg2 = 10V. In the following explanation, the gate voltage may be collectively referred to as Vg.

[0037] Figure 2 shows the current-voltage characteristics of the semiconductor switch SW for the cases Vg=Vg1 and Vg=Vg2, respectively. The horizontal axis in the graph of Figure 2 represents a predetermined terminal voltage in the semiconductor switch SW. In this specification, this voltage is defined as V sw This is how it is written.

[0038] As mentioned above, the semiconductor switch SW may be an FET. In this case, V in the example in Figure 2 sw This represents the drain-source voltage of a FET as a semiconductor switch (SW) (the magnitude of the potential at the drain terminal of the FET relative to the potential at the source terminal of the FET). In the graph in Figure 2, the vertical axis is I in It represents I in This corresponds to the drain current of the FET (the current flowing through the drain terminal of the FET).

[0039] As mentioned above, the semiconductor switch SW may also be an IGBT. In this case, V in the example in Figure 2 sw This represents the collector-emitter voltage of an IGBT as a semiconductor switch (SW) (the magnitude of the potential at the collector terminal of the IGBT relative to the potential at the emitter terminal of the IGBT). And in the example in Figure 2, I in This corresponds to the collector current of the IGBT (the current flowing through the collector terminal of the IGBT).

[0040] As shown in Figure 2, in both the case where Vg=Vg1 and the case where Vg=Vg2, V sw With the increase of I in Vg increases. However, as mentioned above, when Vg = Vg², the semiconductor switch SW operates in the active region. The active region is V sw With the increase of I in Although it increases, in The operating range of semiconductor switches (SW) is where the increase shows a saturation trend.

[0041] On the other hand, in the example in Figure 2, when Vg = Vg1, the semiconductor switch SW operates in the non-active region. In this specification, the non-active region is V sw I in This refers to the operating range of a semiconductor switch (SW) where the increase does not show a saturation trend.

[0042] From these points, V in the case where Vg = Vg² sw I inThe increasing trend of is more gradual compared to the increasing trend in the case of Vg=Vg1 and Vg=Vg2. More specifically, in the example in Figure 2, I in is a constant current value I clamp It saturates at I clamp This is also called clamp current. clamp This is determined according to the specifications of the semiconductor switch SW. For example, I clamp It is preferable that the semiconductor switch SW be selected such that th1 is smaller than th1.

[0043] As described above, the switching control unit 21 controls dI in When / dt is greater than or equal to th2, Vg2, which is lower than Vg1, is supplied to the gate terminal GT. As can be seen from Figure 2, by switching Vg from Vg1 to Vg2, the conduction state of the semiconductor switch SW is maintained, in It can reduce [the problem].

[0044] (effect) Generally, dI in If / dt is large, in There is a high probability that an overshoot is occurring. in (That is, I as an overcurrent) in If this flows into a load, it may cause deterioration or damage to the load. Therefore, it is desirable to protect the load with a DC circuit breaker located upstream of it.

[0045] In the aforementioned Patent Document 1, dI in An example configuration of a DC circuit breaker having a fuse that blows when / dt is large is shown. in If / dt is large, the fuse will blow, I in The signal is interrupted. Thus, in this configuration example, the fuse is used to protect the load from overcurrent.

[0046] However, it generally takes a certain amount of time for the fuse to completely blow. Therefore, in the DC circuit breaker configuration example described in Patent Document 1, there is a risk that an overcurrent may flow into the load for a certain period of time.

[0047] On the other hand, according to the DC circuit breaker 1 of Embodiment 1, Vg is dI in By changing based on / dt, the conduction state of the semiconductor switch SW is changed. in This can reduce the I in to, I clamp From a value greater than I clamp This allows the value to be reduced. In this way, by switching Vg from Vg1 to Vg2, the operating region of the semiconductor switch SW can be shifted from the inactive region to the active region.

[0048] Therefore, unlike the DC circuit breaker in Patent Document 1, DC circuit breaker 1 can protect the load from overcurrent without requiring the fuse to blow. According to DC circuit breaker 1, by changing Vg, I in This can be reduced in a short time. Therefore, DC circuit breaker 1 makes it possible to protect the load more reliably than conventional methods.

[0049] [Embodiment 2] Embodiment 2 describes another configuration example of a DC circuit breaker according to one aspect of the present disclosure. Figure 3 shows an example configuration of a DC power transmission system 100 in Embodiment 2. In the example in Figure 3, the DC power transmission system 100 is equipped with a DC circuit breaker 1A instead of a DC circuit breaker 1.

[0050] DC circuit breaker 1A is equipped with a control unit 20A instead of the control unit 20. In addition to the switching control unit 21, current value comparison unit 22, and current change rate comparison unit 23, the control unit 20A further includes a Joule heat calculation unit 24 and a Joule heat comparison unit 25.

[0051] I in The flow of current generates Joule heat in the semiconductor switch. By considering the Joule heat generated in the semiconductor switch, a wider range of control over the semiconductor switch can be achieved.

[0052] Therefore, the Joule heat calculation unit 24 calculates the Joule heat generated in the semiconductor switch SW. In this specification, the value of Joule heat calculated by the Joule heat calculation unit 24 is denoted as Q. The method for calculating Q by the Joule heat calculation unit 24 is not particularly limited. In Embodiment 2, the Joule heat calculation unit 24 calculates Q during the period when Vg2 is supplied to the gate terminal GT (in other words, the period when the semiconductor switch SW is operating in the active region) based on the I detected by the current sensor. in The examples mainly illustrate cases where calculations are based on [a specific formula / method].

[0053] When Q is relatively large, a relatively large I in It is thought that this current flows through the semiconductor switch SW. Therefore, when Q is relatively large, a relatively large I in It is thought that this current is flowing to the load LD. Therefore, when Q is relatively large, it is preferable to switch the semiconductor switch SW from the conduction state to the disconnection state to protect the load LD.

[0054] Therefore, the Joule thermal comparison unit 25 determines whether or not to switch the semiconductor switch SW from a conductive state to a disconnected state based on Q calculated by the Joule thermal calculation unit 24. As an example, the Joule thermal comparison unit 25 compares Q with a Joule thermal threshold (a threshold for Joule heat). In this specification, the Joule thermal threshold is denoted as th3.

[0055] Specifically, the Joule thermal comparison unit 25 determines whether Q is th3 or greater. That is, the Joule thermal comparison unit 25 uses the following equation (3), Q≧th3 …(3) Determine whether the condition is met.

[0056] If the Joule thermal comparison unit 25 determines that Q is th3 or greater, that is, if it determines that equation (3) is satisfied, it supplies information to the switching control unit 21 indicating that fact.

[0057] The switching control unit 21 switches Vg to Vg0 upon receiving information from the Joule thermal comparison unit 25 indicating that Q is th3 or higher. By supplying Vg0 to the gate terminal GT from the switching control unit 21, the semiconductor switch SW can be switched from a conductive state to a disconnected state. This protects the load LD.

[0058] Q is I in It can be expressed as a quantity proportional to the square of I. From this, Q is I in and the above V sw It can also be expressed as a quantity proportional to the product of . Therefore, the DC circuit breaker 1A in the example of Figure 3 has a voltage sensor 12 in addition to the current sensor 11. The voltage sensor 12 is V sw It just needs to be positioned in a way that allows for detection.

[0059] In the example shown in Figure 3, the voltage sensor 12 detects the potential difference at the first node Np1 relative to the second node Np2, V sw It is detected as such. As mentioned above, the semiconductor switch SW may be an FET. In this case, in the example in Figure 3, the source terminal of the FET acting as the semiconductor switch SW is connected to the second node Np2. On the other hand, the drain terminal of the FET is connected to the first node Np1.

[0060] As mentioned above, the semiconductor switch SW may also be an IGBT. In this case, in the example in Figure 3, the emitter terminal of the IGBT used as the semiconductor switch SW is connected to the second node Np2. On the other hand, the collector terminal of the IGBT is connected to the first node Np1.

[0061] In the example shown in Figure 3, the control unit 20A receives current from the current sensor 11. inIn addition to obtaining the voltage from the voltage sensor 12, V sw To obtain this. In this case, as an example, the Joule heat calculation unit 24 calculates the following equation (4): Q=I in ×V sw ×t Q …(4) Q can be calculated accordingly. Q t represents a predetermined time length. Q The value of may be determined by the designer of the DC circuit breaker 1A, for example, based on the specifications of the semiconductor switch SW. As described above, the Joule heat calculation unit 24 calculates the I detected by the current sensor 11. in and the V detected by the voltage sensor 12 sw Q may be calculated based on this.

[0062] (Example of processing flow in DC circuit breaker 1A) Figure 4 is a flowchart illustrating the processing flow in DC circuit breaker 1A. In the example in Figure 4, the processing in step S2 and the processing in steps S3 to S6 are executed in parallel. Throughout the period in which the series of processes in Figure 4 are executed, the control unit 20A receives current from the current sensor 11. in In addition to obtaining the voltage from the voltage sensor 12, V sw Assume that you have obtained it.

[0063] First, in step S1, the switching control unit 21 supplies Vg1 (first gate voltage) to the gate terminal GT. This allows the semiconductor switch SW to operate in the non-active region.

[0064] In the example in Figure 4, steps S2 and S3 follow step S1, respectively. First, step S2 will be described. In step S2, the current value comparison unit 22 performs I in The current value comparison unit 22 determines whether the value is th1 or greater. That is, it determines whether the above equation (1) is satisfied.

[0065] If the answer is YES in step S2, that is, I inIf it is greater than or equal to th1, the process proceeds to step S7. The processing in step S7 will be described later. On the other hand, if it is NO in step S2, that is, in if I is less than th1, the process returns to step S2. Therefore, until I in reaches th1, step S2 is repeated.

[0066] Next, step S3 will be described. In step S3, the current change rate comparison unit 23 determines whether dI in / dt is greater than or equal to th2. That is, the current change rate comparison unit 23 determines whether the above-mentioned formula (2) is satisfied.

[0067] If it is YES in step S3, that is, if dI in / dt is greater than or equal to th2, the process proceeds to step S4. On the other hand, if it is NO in step S3, that is, if dI in / dt is less than th2, the process returns to step S3. Therefore, until dI in / dt reaches th2, step S3 is repeated.

[0068] In step S4, the switching control unit 21 switches Vg from Vg1 to Vg2 (the second gate voltage). Then, the switching control unit 21 supplies Vg2 to the gate terminal GT. Thereby, the operating region of the semiconductor switch SW can be shifted from the non-active region to the active region.

[0069] Next, in step S5, the joule heat calculation unit 24 calculates the joule heat Q. As an example, the joule heat calculation unit 24 may calculate Q according to the above-mentioned formula (4).

[0070] Next, in step S6, the joule heat comparison unit 25 determines whether Q is greater than or equal to th3. That is, the joule heat comparison unit 25 determines whether the above-mentioned formula (3) is satisfied.

[0071] If the answer in step S6 is YES, that is, if Q is th3 or greater, proceed to step S7. On the other hand, if the answer in step S6 is NO, that is, if Q is less than th3, return to step S1. Therefore, if Q is less than th3, the operating region of the semiconductor switch SW can be returned from the active region to the inactive region.

[0072] As described above, if the answer is YES in step S2 and / or YES in step S6, the process proceeds to step S7. In other words, if at least one of equations (1) and (3) above is satisfied, the process proceeds to step S7. If at least one of equations (1) and (3) is satisfied, it is considered preferable to switch the semiconductor switch SW from the conduction state to the disconnection state to protect the load LD.

[0073] Therefore, in step S7, the switching control unit 21 supplies Vg0 (cut-off gate voltage) to the gate terminal GT. This allows the semiconductor switch SW to be switched from the conduction state to the cut-off state.

[0074] (Example of a time chart for each signal value) Figure 5 shows an example of a time chart for each signal value in Embodiment 2. In Figure 5, reference numeral 510 denotes I in A graph showing the time progression of is shown, and the symbol 520 is dI in The graphs shown illustrate the time progression of / dt, and the graph labeled 530 shows the time progression of Vg. In each graph in Figure 5, the horizontal axis (t) represents time.

[0075] Figure 5 illustrates a case where a short-circuit fault occurs in the DC power transmission system 100. In the example in Figure 5, I in Although dI has reached a value greater than th1, in / dt remains at a value less than th2. Therefore, the example of FIG. 5 shows a case where the above-described equation (1) is satisfied but equation (2) is not satisfied. That is, the example of FIG. 5 shows a case where it is YES in step S2 of FIG. 4 while it is NO in step S3.

[0076] FIG. 6 shows another example of the time chart of each signal value in Embodiment 2. FIG. 6 is a paired figure with FIG. 5. In FIG. 6, a graph showing the time transition of I in is shown at reference numeral 610, a graph showing the time transition of dI in / dt is shown at reference numeral 620, and a graph showing the time transition of Vg is shown at reference numeral 630.

[0077] Also in FIG. 6, the case where a short-circuit accident occurs in the DC power transmission system 100 is illustrated. However, in the example of FIG. 6, the increase in I in accompanying the occurrence of the short-circuit accident is steeper than in the example of FIG. 5. That is, in the example of FIG. 6, dI in / dt is larger than in the example of FIG. 5. More specifically, in the example of FIG. 6, a sharp pulse-shaped dI in / dt waveform having a signal value larger than th2 occurs.

[0078] For this reason, in the example of FIG. 6, Vg decreases from Vg1 to Vg2 due to the occurrence of the said waveform of dI in / dt. As described above, during the period when Vg = Vg2, the semiconductor switch SW operates in the active region. Therefore, the maximum value of I in is maintained at I clamp . Thus, during the period when Vg = Vg2, the maximum value of I in is clamped. From this, the state of the DC circuit breaker 1A during the said period may be referred to as a current clamp state.

[0079] As described above, the example in Figure 6 shows a case where equation (1) above is not satisfied, but equation (2) is satisfied. In addition, the example in Figure 6 shows a case where equation (3) above is satisfied. In Figure 6, Vg2 is supplied to the gate terminal GT for t Q An example is given where, after a certain amount of time has elapsed, it is determined that equation (3) above is satisfied. Therefore, at that point in time, Vg decreases from Vg2 to Vg0.

[0080] [Examples of implementation using software] The function of the DC circuit breakers 1 to 1A (hereinafter referred to as "devices" for convenience) can be realized by a program that causes a computer to function as the device, and by a program that causes a computer to function as each control block of the device (especially each part included in the control units 20 to 20A).

[0081] 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., memory) as hardware for executing the program. By executing the program using this control device and storage device, each of the functions described in each of the embodiments is realized.

[0082] The above program may be recorded on one or more computer-readable recording media, not temporary ones. These recording media may or may not be provided by the above device. In the latter case, the program may be supplied to the above device via any wired or wireless transmission medium.

[0083] Some or all of the functions of each of the above control blocks can also be implemented by logic circuits. For example, an integrated circuit in which logic circuits functioning as each of the above control blocks are formed is also included in one aspect of this disclosure. In addition, it is also possible to implement the functions of each of the above control blocks by, for example, a quantum computer.

[0084] Each of the processes described in the above embodiments may be performed by AI (Artificial Intelligence). In this case, the AI ​​may operate on the control device described above, or it may operate on other devices (e.g., an edge computer or a cloud server).

[0085] 〔summary〕 A DC circuit breaker according to Embodiment 1 of the present disclosure is a DC circuit breaker positioned upstream of a load in a DC power transmission system, and comprises: a semiconductor switch connected to a DC power transmission line in the DC power transmission system and having a gate terminal; a current sensor that detects the current value of the current flowing through the semiconductor switch and the rate of change of the current value over time; and a control unit that controls the semiconductor switch by supplying a gate voltage to the gate terminal, wherein the control unit reduces the current flowing through the semiconductor switch when the semiconductor switch is in a conductive state by changing the gate voltage based on the rate of change of the current detected by the current sensor.

[0086] In the DC circuit breaker according to Embodiment 2 of the present disclosure, in Embodiment 1, the control unit may conduct the semiconductor switch by supplying a first gate voltage as the gate voltage to the gate terminal, and when the rate of change of current detected by the current sensor is greater than or equal to a current rate of change threshold, the control unit may reduce the current flowing through the semiconductor switch while maintaining the conduction state of the semiconductor switch by supplying a second gate voltage lower than the first gate voltage as the gate voltage to the gate terminal.

[0087] In the DC circuit breaker according to aspect 3 of the present disclosure, the semiconductor switch may be operating in the active region when the second gate voltage is supplied to the gate terminal in aspect 2.

[0088] In the DC circuit breaker according to embodiment 4 of the present disclosure, in embodiment 2 or 3, the control unit may calculate the Joule heat generated in the semiconductor switch during the period in which the second gate voltage is supplied to the gate terminal based on the current value detected by the current sensor, and may determine whether or not to switch the semiconductor switch from a conduction state to a disconnection state based on the Joule heat.

[0089] In the DC circuit breaker according to Embodiment 5 of the present disclosure, in Embodiment 4, the control unit may switch the semiconductor switch from a conduction state to a disconnection state by supplying a disconnection gate voltage as the gate voltage to the gate terminal when the Joule heat is equal to or greater than the Joule heat threshold.

[0090] A DC circuit breaker according to embodiment 6 of the present disclosure may further include a voltage sensor that detects a predetermined terminal voltage value in the semiconductor switch, and the control unit may calculate the Joule heat based on the current value detected by the current sensor and the voltage value detected by the voltage sensor.

[0091] In the DC circuit breaker according to embodiment 7 of the present disclosure, in any one of embodiments 1 to 6, the semiconductor switch may be made to conduct by supplying a first gate voltage as the gate voltage to the gate terminal, and when the current value is equal to or greater than the current threshold, the semiconductor switch may be switched from a conduction state to a disconnection state by supplying a disconnection gate voltage as the gate voltage to the gate terminal.

[0092] A DC power transmission system according to aspect 8 of the present disclosure may include a DC circuit breaker according to any one of aspects 1 to 7, and the load located downstream of the DC circuit breaker.

[0093] [Additional Notes] One aspect of this disclosure is not limited to the embodiments described above, 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 within the technical scope of one aspect of this disclosure. [Explanation of Symbols]

[0094] 1.1A DC circuit breaker 11 Current Sensor 12 Voltage Sensor 20,20A Control Unit 21 Switching Control Unit 22 Current Value Comparison Section 23 Current Change Rate Comparison Section 24 Joule heat calculation unit 25 Joule Heat Comparison Section 81 DC transmission lines 100 DC power transmission systems SW Semiconductor Switch LD load

Claims

1. A DC circuit breaker located upstream of the load in a DC power transmission system, A semiconductor switch connected to a DC power transmission line in the aforementioned DC power transmission system and having a gate terminal, A current sensor that detects the current value of the current flowing through the semiconductor switch and the rate of change of the current value over time, The system includes a control unit that controls the semiconductor switch by supplying a gate voltage to the gate terminal, The control unit reduces the current flowing through the semiconductor switch when the semiconductor switch is in a conductive state by changing the gate voltage based on the rate of change of current detected by the current sensor, thereby providing a DC circuit breaker.

2. The control unit, By supplying the first gate voltage as the gate voltage to the gate terminal, the semiconductor switch is made to conduct. The DC circuit breaker according to claim 1, wherein, when the rate of change of current detected by the current sensor is greater than or equal to a current rate of change threshold, a second gate voltage lower than the first gate voltage is supplied to the gate terminal as the gate voltage, thereby reducing the current flowing through the semiconductor switch while maintaining the conduction state of the semiconductor switch.

3. The DC circuit breaker according to claim 2, wherein the semiconductor switch is operating in the active region when the second gate voltage is supplied to the gate terminal.

4. The control unit, The Joule heat generated in the semiconductor switch during the period in which the second gate voltage is supplied to the gate terminal is calculated based on the current value detected by the current sensor. A DC circuit breaker according to claim 2 or 3, wherein it determines whether or not to switch the semiconductor switch from a conductive state to a disconnected state based on the Joule heat.

5. The DC circuit breaker according to claim 4, wherein the control unit switches the semiconductor switch from a conduction state to a disconnection state by supplying a disconnection gate voltage as the gate voltage to the gate terminal when the Joule heat is equal to or greater than the Joule heat threshold.

6. The DC circuit breaker further includes a voltage sensor that detects a voltage value of a predetermined terminal voltage in the semiconductor switch. The DC circuit breaker according to claim 4, wherein the control unit calculates the Joule heat based on the current value detected by the current sensor and the voltage value detected by the voltage sensor.

7. The control unit, By supplying the first gate voltage as the gate voltage to the gate terminal, the semiconductor switch is made to conduct. The DC circuit breaker according to claim 1, wherein when the current value is greater than or equal to a current threshold, the semiconductor switch is switched from a conduction state to a disconnection state by supplying a disconnection gate voltage as the gate voltage to the gate terminal.

8. A DC circuit breaker according to claim 1, A DC power transmission system comprising the load located downstream of the DC circuit breaker.

Images