Semiconductor circuit breaker

Abstract

This semiconductor circuit breaker (1) comprises a cutoff module (100) and a controller (6). The cutoff module (100) includes a semiconductor element, and a current limiting element that reduces current flowing through an electric circuit connecting a power source and a load. When the energization of the semiconductor element is on, the electric circuit is energized, and the current of the electric circuit is cut off by switching the energization of the semiconductor element from on to off. The controller (6) controls the cutoff module (100) and estimates at least one among a resistance value of the electric circuit and an inductance value of the electric circuit by using a feature value extracted from one or more of a power supply voltage of the electric circuit, element characteristics of the current limiting element, and a current waveform of the electric circuit.

Description

semiconductor circuit breaker

[0001] The present disclosure relates to semiconductor circuit breakers for protecting electrical circuits.

[0002] In a power transmission system that transmits power supplied from a power source to a load, the current that flows in the electrical circuit connecting the power source and the load in the event of a short-circuit accident is called a fault current. A known circuit breaker that interrupts fault current is a semiconductor circuit breaker that uses a semiconductor element to interrupt the fault current. A semiconductor circuit breaker is also called a solid-state circuit breaker (SSCB). A semiconductor circuit breaker uses a semiconductor element to interrupt the current flowing in the electrical circuit for the purpose of protecting the power converter, load, wiring, etc. that constitute the electrical circuit of the power transmission system. The semiconductor element allows current to flow through the electrical circuit in the on state and interrupts the electrical circuit in the off state. When a fault current is detected in the event of a short-circuit accident, the semiconductor circuit breaker performs an interruption operation by switching the semiconductor element from on to off.

[0003] The magnitude of the fault current caused by a short circuit is typically several times the rated current of the electrical circuit. Because the current-withstanding capacity of the semiconductor elements used in semiconductor circuit breakers is small, it is necessary to turn off the semiconductor elements before the fault current caused by a short circuit exceeds the current-withstanding capacity of the semiconductor elements. For example, if the current-withstanding capacity of the semiconductor elements used in a semiconductor circuit breaker is twice the rated current, the semiconductor elements must be turned off before the fault current caused by a short circuit reaches twice the rated current. Furthermore, when a load connected to an electrical circuit is turned on, an inrush current that exceeds the rated current may transiently flow. Because the occurrence of this inrush current is a normal phenomenon and not due to a short circuit, semiconductor circuit breakers are required not to perform an interruption operation in response to the inrush current.

[0004] The magnitude of an inrush current may exceed twice the rated current of an electric circuit. To prevent such an inrush current from exceeding the current-withstanding capacity of a semiconductor element, it is conceivable to use a semiconductor element with a high rated capacity. However, the higher the rated capacity of the semiconductor element used in a semiconductor circuit breaker, the higher the cost of the semiconductor circuit breaker. Therefore, in order to enable the use of semiconductor elements with a low rated capacity, current limiting is sometimes performed to reduce the inrush current during closing operation so that the inrush current does not exceed the current-withstanding capacity. Patent Document 1 discloses a semiconductor circuit breaker with a current limiting function that reduces inrush current by repeatedly turning a semiconductor element on and off based on a measured current value.

[0005] Special Publication No. 5-506120

[0006] According to the technology of Patent Document 1, current limiting is performed before the current flowing through the electric circuit increases, making it difficult to determine whether the state of the electric circuit is a short circuit state or an overload state during the closing operation. If it is not possible to distinguish between a short circuit state and an overload state, it becomes difficult to determine the location and cause of the accident when restoring the electric circuit.

[0007] The present disclosure has been made in view of the above, and aims to provide a semiconductor circuit breaker that can easily distinguish between a short circuit state and an overload state.

[0008] To solve the above-mentioned problems and achieve the object, the semiconductor circuit breaker according to the present disclosure includes a circuit breaking module and a controller. The circuit breaking module has a semiconductor element and a current limiting element that reduces a current flowing in an electric circuit connecting a power source and a load, and energizes the electric circuit when the semiconductor element is on, and interrupts the current in the electric circuit by switching the semiconductor element from on to off. The controller controls the circuit breaking module and estimates at least one of a resistance value and an inductance value of the electric circuit using feature quantities extracted from one or more of the power supply voltage of the electric circuit, the element characteristics of the current limiting element, and the current waveform of the electric circuit.

[0009] The semiconductor circuit breaker according to the present disclosure has the effect of making it possible to easily distinguish between a short-circuit state and an overload state.

[0010] FIG. 1 is a diagram showing an example of a power transmission system incorporating a semiconductor circuit breaker according to embodiment 1; FIG. 2 is a diagram showing a single-pole structure of a semiconductor circuit breaker according to embodiment 1; FIG. 3 is a circuit diagram of a circuit breaker module constituting the semiconductor circuit breaker according to embodiment 1; FIG. 4 is a diagram showing an example of a current waveform in the circuit breaker module of the semiconductor circuit breaker according to embodiment 1; FIG. 5 is a first diagram for explaining a current path in the circuit breaker module of the semiconductor circuit breaker according to embodiment 1; FIG. 6 is a second diagram for explaining a current path in the circuit breaker module of the semiconductor circuit breaker according to embodiment 1; FIG. 7 is a diagram showing a state of an electric circuit when the semiconductor circuit breaker according to embodiment 1 is operated;

[0011] Hereinafter, a semiconductor circuit breaker according to an embodiment will be described in detail with reference to the drawings.

[0012] First Embodiment. Fig. 1 is a diagram showing an example of a power transmission system 10 incorporating a semiconductor circuit breaker 1 according to a first embodiment. The power transmission system 10 is a system that transmits power supplied from a power source to each of a plurality of loads 4. The semiconductor circuit breaker (SSCB) 1 is incorporated into an electric circuit that connects the power source and the loads 4. Fig. 1 is a single-line diagram that schematically shows an electric circuit incorporating the semiconductor circuit breaker 1. The semiconductor circuit breaker 1 interrupts a fault current that flows through the electric circuit in the event of a short-circuit fault. The power source is not shown in Fig. 1.

[0013] Electric power from the grid is sent to the power receiving equipment of the consumer via a transformer 2. The power, whose voltage has been converted by the transformer 2, is supplied to each load 4 via a distribution line 3. FIG. 1 shows an example of a distribution network in which a load 4 is connected to each of a plurality of distribution lines 3. The number of loads 4 connected to the distribution network is arbitrary. Each distribution line 3 includes a resistance 31 and an inductance 32 according to the length of the distribution line 3. Each load 4 includes a resistance 41 and an inductance 42. A semiconductor circuit breaker 1 is arranged between the transformer 2 and the distribution line 3. A circuit breaker (CB) 5 is arranged between the distribution line 3 and the load 4.

[0014] In the distribution network shown in Figure 1, if a short circuit occurs in one load 4, the circuit breaker 5 and semiconductor circuit breaker 1, which are located between the load 4 at the fault point 7 where the short circuit occurred and the distribution line 3, operate to interrupt the fault current. By interrupting the fault current, the distribution line 3 and the load 4 are protected.

[0015] Fig. 2 is a diagram showing a single-pole structure of the semiconductor circuit breaker 1 according to the first embodiment. In the first embodiment, the semiconductor circuit breaker 1 is a circuit breaker compatible with three-phase AC. The single-pole structure shown in Fig. 2 is a structure that is responsible for energizing and blocking current for each phase. The semiconductor circuit breaker 1 is provided with three structures shown in Fig. 2 corresponding to the three power lines of the U phase, V phase, and W phase.

[0016] The single-pole structure of the semiconductor circuit breaker 1 shown in Figure 2 includes a controller 6 and two interrupting modules 100. Each interrupting module 100 has a semiconductor element and a current-limiting element. When the semiconductor element is turned on, each interrupting module 100 energizes an electric circuit connecting a power source and a load 4. Each interrupting module 100 interrupts the current in the electric circuit by switching the conduction of the semiconductor element from on to off. The controller 6 controls each interrupting module 100.

[0017] 3 is a circuit diagram of a circuit breaking module 100 constituting the semiconductor circuit breaker 1 according to embodiment 1. The circuit breaking module 100 includes a semiconductor element 101, a diode 102, a nonlinear element 103, a gate power supply 104, a shunt resistor 105, a disconnection switch 106, and an overcurrent detection circuit 200.

[0018] The semiconductor element 101 has a unidirectional blocking capability. The semiconductor element 101 is, for example, a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT). If the semiconductor element 101 is a MOSFET, the terminal 111 is a drain terminal and the terminal 112 is a source terminal. If the semiconductor element 101 is an IGBT, the terminal 111 is a collector terminal and the terminal 112 is an emitter terminal. The semiconductor element 101 can block only current of the polarity flowing from the terminal 111 to the terminal 112.

[0019] In order to provide the semiconductor circuit breaker 1 with a bidirectional breaking capability that can break both forward and reverse currents, the semiconductor circuit breaker 1 is configured such that the terminal 111 of one semiconductor element 101 faces the terminal 111 of another semiconductor element 101, and the two semiconductor elements 101 are connected in series, as shown in Fig. 2. Alternatively, the two semiconductor elements 101 may be connected in series such that the terminal 112 of one semiconductor element 101 faces the terminal 112 of the other semiconductor element 101.

[0020] The diode 102 is connected in parallel to the semiconductor element 101. The diode 102 bypasses current in a direction that the semiconductor element 101 cannot block. The non-linear element 103 is connected in parallel to the semiconductor element 101. The non-linear element 103 has a non-linear current-voltage characteristic. The non-linear element 103 functions as a current-limiting element that reduces the current flowing through the electric circuit. The non-linear element 103 is, for example, a Zener diode or a varistor.

[0021] The gate power supply 104 applies a voltage to the terminal 113 of the semiconductor element 101. The terminal 113 is a gate terminal. When the gate power supply 104 applies a voltage to the terminal 113, the semiconductor element 101 is in an ON state. When the semiconductor element 101 is in an ON state, it energizes the electric circuit. When no voltage is applied to the terminal 113, the semiconductor element 101 is in an OFF state. When the semiconductor element 101 is in an OFF state, it interrupts the electric circuit. The semiconductor element 101 is switched ON and OFF by applying a voltage to the terminal 113 and stopping the application of the voltage to the terminal 113. The shunt resistor 105 is connected to the terminal 112. The shunt resistor 105 is a current measuring instrument that detects the magnitude of the current flowing through the electric circuit. The disconnection switch 106 is connected to the terminal 111.

[0022] The controller 6 extracts features of the current waveform by digitally processing the signal based on the current signal s1 received from each interruption module 100. The controller 6 also controls the gate power supply 104 of each interruption module 100 by outputting a gate control signal s2 to each interruption module 100.

[0023] The controller 6 estimates at least one of the resistance value and the inductance value of the electric circuit using feature quantities extracted from one or more of the power supply voltage of the electric circuit, the element characteristics of the current limiting element, and the current waveform of the electric circuit. The estimation of the resistance value and the inductance value by the controller 6 will be described later.

[0024] A terminal 211 of the overcurrent detection circuit 200 is connected to one end of the shunt resistor 105. A terminal 212 of the overcurrent detection circuit 200 is connected to the other end of the shunt resistor 105. The overcurrent detection circuit 200 measures the voltage across the shunt resistor 105 to measure the current flowing through the interrupter module 100.

[0025] Terminal 213 of overcurrent detection circuit 200 is connected to terminal 113 of semiconductor element 101. When the current flowing through interrupting module 100 exceeds an overcurrent threshold, which is a criterion for determining an overcurrent, overcurrent detection circuit 200 shorts terminal 211 and terminal 213. This short-circuiting between terminal 211 and terminal 213 shorts gate power supply 104, turning semiconductor element 101 off. Subsequently, when the current flowing through interrupting module 100 becomes smaller than the overcurrent threshold, overcurrent detection circuit 200 opens terminal 211 and terminal 213. This opening between terminal 211 and terminal 213 resumes the application of voltage to terminal 113 by gate power supply 104, turning semiconductor element 101 on. Note that in FIG. 3 , the shorting or opening between terminal 211 and terminal 213 by overcurrent detection circuit 200 is indicated by a dashed line in overcurrent detection circuit 200.

[0026] Next, the operation of the interrupting module 100 when a short circuit occurs in an electric circuit will be described. Fig. 4 is a diagram showing an example of a current waveform in the interrupting module 100 of the semiconductor circuit breaker 1 according to the first embodiment. Fig. 4 also shows a graph representing a change in the magnitude of current after a short circuit occurs. In the graph shown in Fig. 4, the vertical axis represents current and the horizontal axis represents time. In the following description, the variable representing time is referred to as "t".

[0027] Fig. 5 is a first diagram for explaining the current path in the interrupting module 100 of the semiconductor circuit breaker 1 according to the first embodiment. Fig. 6 is a second diagram for explaining the current path in the interrupting module 100 of the semiconductor circuit breaker 1 according to the first embodiment. In Fig. 5 and Fig. 6, dashed arrows marked "cur" represent current paths. Fig. 5 shows the current path when t<t2 in the graph shown in Fig. 4. Fig. 6 shows the current path when t2<t<t3 in the graph shown in Fig. 4.

[0028] Before a short circuit occurs, the semiconductor element 101 is in an ON state. At this time, in the interrupting module 100, current flows through a path that passes through the semiconductor element 101, as shown in FIG. 5 . When a short circuit occurs, the current flowing through the interrupting module 100 increases. t1 is defined as the time when the current value of the current flowing through the interrupting module 100 reaches i2, which is an overcurrent threshold. i2, which is set in advance. When the time reaches t1 and the current value exceeds i2, the overcurrent detection circuit 200 operates to short-circuit terminals 211 and 213. The short-circuit between terminals 211 and 213 switches the semiconductor element 101 from ON to OFF.

[0029] The overcurrent detection circuit 200 operates very fast, but the switching of the semiconductor element 101 from on to off is completed with a slight delay from t1. This delay is due to the presence of stray capacitance in the electric circuit, etc. t2 is the time when the switching of the semiconductor element 101 from on to off is completed. As shown in FIG. 4, the current value reaches a maximum value at t=t2. This maximum value is the first current value. The first current value is the current value of the current flowing through the electric circuit at the first time. The first time is the time after a delay time has elapsed since the value of the current flowing through the electric circuit exceeded the overcurrent threshold, which is the criterion for determining an overcurrent. In the first embodiment, the delay time is a preset time. In the example shown in FIG. 4, c1 is the first current value. t2 is the first time.

[0030] When the semiconductor element 101 is turned off at time t=t2, the current path is switched from the path passing through the semiconductor element 101 to the path passing through the nonlinear element 103. When the current path is switched to the path passing through the nonlinear element 103, the current decreases in the nonlinear element 103. That is, the current value of the current flowing through the interruption module 100 decreases from c1 at time t2.

[0031] When the current value becomes smaller than i2, the overcurrent detection circuit 200 operates to open the gap between the terminals 211 and 213. Opening the gap between the terminals 211 and 213 switches the semiconductor element 101 from off to on. The switching of the semiconductor element 101 from off to on is completed with a delay from when the current value reaches i2. t3 is the time when the switching of the semiconductor element 101 from off to on is completed. As shown in FIG. 4 , the current value reaches a minimum value at t=t3. This minimum value is the second current value. The second current value is the current value of the current flowing through the electric circuit at the second time. The second time is the time after a delay time has elapsed since the value of the current flowing through the electric circuit fell below the overcurrent threshold. In the example shown in FIG. 4 , c2 is the second current value. t3 is the second time.

[0032] At t=t3, semiconductor element 101 is turned on, switching the current path from the path through nonlinear element 103 to the path through semiconductor element 101. When the current path is switched to the path through semiconductor element 101, the current flowing through interruption module 100 rises again.

[0033] When the current value exceeds i2, the semiconductor element 101 is switched from on to off, and then when the current value becomes smaller than i2, the semiconductor element 101 is switched from off to on. Until the fault current caused by the short circuit fault is removed, the current rises while the semiconductor element 101 is in the on state. By repeatedly turning the semiconductor element 101 on and off until the fault current is removed, the current value of the current flowing through the interrupting module 100 is maintained near i2. In this way, when a short circuit fault occurs, the interrupting module 100 performs a current limiting maintaining operation that maintains the current value by repeatedly turning the semiconductor element 101 on and off until the fault current is removed.

[0034] Here, the fault determination threshold, which is a threshold for determining whether the current flowing through the electric circuit is a fault current or an inrush current when the current value exceeds i2, is defined as i1. i1 is a value smaller than i2. The fault determination threshold i1 is set in advance. For example, the rated current value of the electric circuit is set as i1.

[0035] When a fault current occurs, the current value is maintained near i2 while the semiconductor element 101 is repeatedly turned on and off. Furthermore, when td has elapsed since t=t1, i.e., at t=t1+td, the current value is greater than i1. td is a preset fault determination time. The controller 6 determines that a fault current has occurred when the current value is greater than i1 at t=t1+td. In other words, the controller 6 determines that a short-circuit fault has occurred. The controller 6 makes this determination based on the current signal s1 received from the interrupter module 100.

[0036] When the controller 6 determines that a short circuit has occurred, it outputs a gate control signal s2 to the interrupter module 100 to turn off the gate power supply 104. This causes the semiconductor circuit breaker 1 to turn off the semiconductor element 101. Furthermore, the nonlinear element 103 performs current limiting until the current becomes zero. The semiconductor circuit breaker 1 turns off the semiconductor element 101 and completely interrupts the current by limiting the current in the nonlinear element 103.

[0037] Next, a method for estimating the value of the resistance R of the electric circuit and the value of the inductance L of the electric circuit will be described. FIG. 7 is a diagram showing the state of the electric circuit when the semiconductor circuit breaker 1 according to the first embodiment operates. FIG. 8 is a diagram for explaining the feature quantities extracted from the current waveform according to the first embodiment. FIG. 7 shows a state in which the power supply 11, the semiconductor circuit breaker 1, and the resistance 12 and inductance 13 of the electric circuit are connected in series. FIG. 8 shows an example of a current waveform in the electric circuit. The current waveform shown in FIG. 8 is a current waveform when the semiconductor circuit breaker 1 operates due to a short-circuit fault.

[0038] 7 , when the semiconductor circuit breaker 1 operates, a voltage V is applied across the semiconductor circuit breaker 1. The controller 6 measures the voltage V. The power supply voltage E of the electric circuit is also measured in real time, and the value of the power supply voltage E is input to the controller 6. The current I flowing through the electric circuit is measured by the shunt resistor 105 of the semiconductor circuit breaker 1. The value of the current I is input to the controller 6.

[0039] From FIG. 7, the equation of the electric circuit is expressed by the following formula (1): L(dI / dt)=EV-RI (1)

[0040] By substituting the values ​​of the power supply voltage E, dI / dt, and voltage V into equation (1) when semiconductor circuit breaker 1 is in the on state and equation (1) when semiconductor circuit breaker 1 is in the off state, two equations are obtained in which the values ​​of resistance R and inductance L are unknowns. Controller 6 can estimate the values ​​of resistance R and inductance L by solving the simultaneous equations consisting of these two equations.

[0041] Here, the feature quantities used to estimate the values ​​of resistance R and inductance L will be specifically described. As shown in FIG. 8 , the current increases due to the occurrence of a short-circuit fault, and at t=t1, the current value exceeds the overcurrent threshold i2. At t=t2, which is the time delay Δt after t1, the semiconductor element 101 switches from on to off. After t2, the current decreases due to commutation, in which the current path is switched from the semiconductor element 101 to the nonlinear element 103. Since the current decreases after t2, the current value reaches a maximum value at t2. This maximum value is c1. Because the semiconductor element 101 operates at high speed, the delay time Δt is small, and the change in the current value in the range t1<t<t2 can be considered small. Therefore, the value of the current I in equation (1) can be approximated to i2. In other words, it is considered that I=i2 holds.

[0042] Substituting I = i2 into equation (1) gives the following equation (2). Equation (2) is an equation for an electric circuit when t1 < t < t2. Note that since the semiconductor element 101 is in the on state when t1 < t < t2, the voltage V across the semiconductor circuit breaker 1 can be considered to be zero. L(dI / dt) = E - Ri2 (2)

[0043] dI / dt can be approximated by the following equation (3) using c1, which is the maximum current value, Δt, and i2, which is the overcurrent threshold value: dI / dt=(c1-i2)Δt (3)

[0044] The value of the power supply voltage E and i2 are all known values. The delay time Δt is determined based on the characteristics of the semiconductor element 101, the characteristics of the overcurrent detection circuit 200, and the characteristics of the gate power supply 104. In other words, the delay time Δt is a known value. Therefore, the value of the resistance R and the value of the inductance L are unknown quantities in equation (2).

[0045] Next, we will explain the equation for the electric circuit when t2<t<t3. When t2<t<t3, the semiconductor element 101 is in the off state, and current flows through the nonlinear element 103. A voltage V determined by the characteristics of the nonlinear element 103 is applied across the semiconductor circuit breaker 1. The current flowing through the electric circuit decreases due to the voltage V determined based on the characteristics of the nonlinear element 103. In other words, current limiting occurs in the electric circuit due to the characteristics of the nonlinear element 103. The current decreases, and at t=t1', the current value falls below i2. At t=t3, when a delay time Δt has elapsed from t1', the semiconductor element 101 switches from off to on. After t3, the current path is returned from the nonlinear element 103 to the semiconductor element 101, causing the current to increase. Since the current increases after t3, the current value reaches a minimum value at t3. This minimum value is c2.

[0046] When t2<t<t3, the value of current I can be approximated to i2, just as when t1<t<t2. Substituting I=i2 into equation (1) gives the following equation (4). Equation (4) is the equation for the electric circuit when t2<t<t3. L(dI / dt)=E-V-Ri2 (4)

[0047] dI / dt can be approximated by the following equation (5) using c2, which is the minimum current value, Δt, and i2, which is the overcurrent threshold value: dI / dt=(c2-i2)Δt (5)

[0048] The value of the power supply voltage E, i2, and the delay time Δt are all known values. Therefore, the value of the resistance R and the value of the inductance L are unknowns in equation (4).

[0049] The controller 6 calculates the value of resistance R and the value of inductance L by solving a simultaneous equation that combines equation (2), which is an equation for t1 < t < t2 when the semiconductor element 101 is in the on state, and equation (4), which is an equation for t2 < t < t3 when the semiconductor element 101 is in the off state.

[0050] As described above, the controller 6 estimates the values ​​of the resistance R and the inductance L using the value of the power supply voltage E, the value of the voltage V generated by the nonlinear element 103, the value of the delay time Δt, the first current value c1, the second current value c2, and the overcurrent threshold i2. That is, the feature quantities used to estimate the values ​​of the resistance R and the inductance L include the value of the power supply voltage E, the value of the voltage V generated by the nonlinear element 103, the value of the delay time Δt, the first current value c1, the second current value c2, and the overcurrent threshold i2.

[0051] The value of the power supply voltage E is a feature extracted from the power supply voltage E of the electric circuit. The value of the voltage V is a feature extracted from the element characteristics of the nonlinear element 103, which is a current limiting element. The first current value c1 and the second current value c2 are feature extracted from the current waveform of the electric circuit. The value of the delay time Δt and the overcurrent threshold i2 are feature values ​​that are set in advance. The controller 6 estimates the resistance value and the inductance value of the electric circuit using the feature extracted from each of the power supply voltage E of the electric circuit, the element characteristics of the current limiting element, and the current waveform of the current circuit.

[0052] Once the resistance and inductance values ​​of the electric circuit are determined, it becomes possible to determine whether the state of the electric circuit is a short circuit or an overload state during the closing operation. If the resistance and inductance values ​​of the electric circuit are both very small, it can be assumed that a short circuit has occurred. On the other hand, if the resistance and inductance values ​​of the electric circuit are both very large, it can be assumed that the load 4 is in an overload state and an overcurrent has occurred.

[0053] The controller 6 may determine whether the electric circuit is in a short-circuit state or an overload state based on the estimated resistance value and the estimated inductance value. In this case, the controller 6 may determine that the electric circuit is in a short-circuit state when the estimated resistance value is less than a predetermined threshold value and the estimated inductance value is less than a predetermined threshold value. In this way, by the controller 6 estimating the resistance value and the inductance value, the semiconductor circuit breaker 1 can easily determine whether it is in a short-circuit state or an overload state.

[0054] The controller 6 may also determine whether the electric circuit is in a short-circuit state or an overload state based on the current signal s1 received from the interrupting module 100, the estimated resistance value, and the estimated inductance value. That is, the controller 6 may determine whether the electric circuit is in a short-circuit state or an overload state based on the current value of the current flowing through the electric circuit at t = t1 + td, the estimated resistance value, and the estimated inductance value. In this case, the controller 6 may determine that the electric circuit is in a short-circuit state when the current value is greater than i1, the estimated resistance value is less than a predetermined threshold, and the estimated inductance value is less than a predetermined threshold. In this way, the semiconductor circuit breaker 1 can easily determine whether the electric circuit is in a short-circuit state or an overload state based on the estimated resistance value, the estimated inductance value, and the current value of the current flowing through the electric circuit.

[0055] When the controller 6 determines that the electric circuit is in a short-circuit state, the controller 6 may send a gate control signal s2, which is a control command, to the interrupting module 100 to cause the interrupting module 100 to interrupt the current in the electric circuit. This allows the semiconductor circuit breaker 1 to interrupt the current in the electric circuit when it determines that the electric circuit is in a short-circuit state.

[0056] In the above description, the controller 6 estimates the resistance value and the inductance value of the electric circuit using feature quantities extracted from the power supply voltage E of the electric circuit, the element characteristics of the current limiting element, and the current waveform of the current circuit. The feature quantities used for the estimation may be feature quantities extracted from one or more of the power supply voltage E of the electric circuit, the element characteristics of the current limiting element, and the current waveform of the current circuit. Furthermore, the controller 6 may estimate at least one of the resistance value and the inductance value of the electric circuit using the feature quantities. In other words, the controller 6 may estimate at least one of the resistance value and the inductance value of the electric circuit using feature quantities extracted from one or more of the power supply voltage E of the electric circuit, the element characteristics of the current limiting element, and the current waveform of the current circuit.

[0057] According to the first embodiment, the semiconductor circuit breaker 1 estimates at least one of the resistance value and the inductance value of the electric circuit using feature quantities extracted from one or more of the power supply voltage E of the electric circuit, the element characteristics of the current limiting element, and the current waveform of the electric circuit. By estimating at least one of the resistance value and the inductance value of the electric circuit, the semiconductor circuit breaker 1 can easily determine whether the state of the electric circuit is a short-circuit state or an overload state during a closing operation. As described above, the semiconductor circuit breaker 1 has the effect of easily distinguishing between a short-circuit state and an overload state. By being able to easily distinguish between a short-circuit state and an overload state, it becomes possible to easily determine the location and cause of the accident when restoring the electric circuit.

[0058] 9 is a circuit diagram of a circuit breaker module 100A constituting a semiconductor circuit breaker 1 according to embodiment 2. In embodiment 2, the same components as those in embodiment 1 above are assigned the same reference numerals, and the following description will focus on the configuration that differs from embodiment 1.

[0059] 3 , the interrupting module 100A includes a semiconductor element 101, a diode 102, a nonlinear element 103, a gate power supply 104, a shunt resistor 105, a disconnection switch 106, and an overcurrent detection circuit 200. The interrupting module 100A further includes a resistive element 107 and a switch 108. The resistive element 107 and the switch 108 are connected in series with each other. The resistive element 107 and the switch 108 are connected in parallel with the semiconductor element 101. The resistive element 107 functions as a current limiting element that reduces the current flowing through the electric circuit.

[0060] Next, the operation of the interrupting module 100A when a short circuit occurs in the electric circuit will be described. An example of a current waveform in the interrupting module 100A after a short circuit occurs is the same as the current waveform shown in Figure 4. An example of a current waveform in the current circuit when the semiconductor circuit breaker 1 operates due to a short circuit is the same as the current waveform shown in Figure 8.

[0061] Fig. 10 is a first diagram for explaining the current path in the interrupting module 100A of the semiconductor circuit breaker 1 according to the second embodiment. Fig. 11 is a second diagram for explaining the current path in the interrupting module 100A of the semiconductor circuit breaker 1 according to the second embodiment. In Fig. 10 and Fig. 11, dashed arrows marked "cur" indicate the current path. Fig. 10 shows the current path when t<t2 in the graph shown in Fig. 4. Fig. 11 shows the current path when t2<t<t3 in the graph shown in Fig. 4.

[0062] Before a short circuit occurs, the semiconductor element 101 is in an ON state. At this time, in the interruption module 100A, a current flows through a path passing through the semiconductor element 101 as shown in FIG. 10. When a short circuit occurs, the current flowing through the interruption module 100A increases. As in the first embodiment, the semiconductor element 101 is in an ON state when t<t2.

[0063] At t=t2, the semiconductor element 101 switches from on to off. As in the first embodiment, the semiconductor element 101 is in the off state when t2<t<t3. After t2, the current decreases due to commutation, in which the current path is switched from the semiconductor element 101 to the resistor element 107. Current limiting occurs in the electric circuit due to the characteristics of the resistor element 107. When a short-circuit fault occurs, the interrupter module 100A performs a current limiting maintaining operation to maintain the current value by repeatedly turning the semiconductor element 101 on and off until the fault current is removed.

[0064] As in the first embodiment, the controller 6 compares the current value at t = t1 + td with i1 to determine whether the current flowing through the electrical circuit is a fault current or an inrush current. If the controller 6 determines that a short-circuit fault has occurred, it outputs a gate control signal s2 to the interrupter module 100A to turn off the gate power supply 104. This causes the semiconductor circuit breaker 1 to turn off the semiconductor element 101. Furthermore, the controller 6 switches the switch 108 from on to off. By turning off the switch 108, the semiconductor circuit breaker 1 interrupts the current flowing through the resistance element 107. By turning off the semiconductor element 101 and the switch 108, the semiconductor circuit breaker 1 completely interrupts the current.

[0065] Let the resistance value of the resistive element 107 be r. The voltage V can be approximated to ri2. Substituting V=ri2 into the above equation (4) gives the following equation (6). Note that in the second embodiment, as in the first embodiment, the value of the current I can be approximated to i2. L(dI / dt)=E-ri2-Ri2 (6)

[0066] The controller 6 calculates the value of resistance R and the value of inductance L by solving a simultaneous equation that combines the above equation (2), which is an equation for t1 < t < t2 when the semiconductor element 101 is in the on state, and equation (6), which is an equation for t2 < t < t3 when the semiconductor element 101 is in the off state.

[0067] As described above, the controller 6 estimates the resistance R and the inductance L using the power supply voltage E, the resistance value r of the resistive element 107, the delay time Δt, the first current value c1, the second current value c2, and the overcurrent threshold i2. That is, the feature quantities used to estimate the resistance R and the inductance L include the power supply voltage E, the resistance value r of the resistive element 107, the delay time Δt, the first current value c1, the second current value c2, and the overcurrent threshold i2. The resistance value r is a feature quantity extracted from the element characteristics of the resistive element 107, which is a current limiting element. The controller 6 estimates the resistance and inductance values ​​of the electric circuit using feature quantities extracted from the power supply voltage E of the electric circuit, the element characteristics of the current limiting element, and the current waveform of the current circuit.

[0068] The resistive element 107 has a higher energy tolerance than the nonlinear element 103, such as a Zener diode or a varistor. The semiconductor circuit breaker 1 is capable of maintaining a current limiting state for a long period of time by using the resistive element 107 as a current limiting element.

[0069] The controller 6 may estimate at least one of the resistance value of the electric circuit and the inductance value of the electric circuit using features extracted from one or more of the power supply voltage E of the electric circuit, the element characteristics of the current limiting element, and the current waveform of the current circuit.

[0070] According to the second embodiment, the semiconductor circuit breaker 1 has the effect of being able to easily distinguish between a short circuit state and an overload state, similar to the case of the first embodiment. Furthermore, according to the second embodiment, the semiconductor circuit breaker 1 can perform a current limiting maintaining operation for a long period of time.

[0071] Embodiment 3. Figure 12 is a diagram showing an example of a current waveform in the interruption module of a semiconductor circuit breaker 1 according to embodiment 3. In embodiment 3, the same components as those in embodiment 1 or 2 above are assigned the same reference numerals, and the following description will mainly focus on the configuration that differs from embodiment 1 or 2.

[0072] The interrupting module of the semiconductor circuit breaker 1 according to the third embodiment has a configuration similar to that of the interrupting module 100 according to the first embodiment or that of the interrupting module 100A according to the second embodiment. In the following description, the semiconductor circuit breaker 1 according to the third embodiment has a configuration similar to that of the interrupting module 100 according to the first embodiment. In the third embodiment, the interrupting module 100 does not repeatedly turn on and off the semiconductor element 101 when a short circuit fault occurs. In the third embodiment, the semiconductor element 101 remains in the off state after switching from on to off.

[0073] When time t1 arrives and the current value exceeds i2, the overcurrent detection circuit 200 operates to switch the semiconductor element 101 from on to off. After the semiconductor element 101 switches to the off state at t=t2, the semiconductor element 101 remains in the off state. The current path is switched to a path that passes through the nonlinear element 103, and the current value in the electric circuit continues to decrease. When the current value in the electric circuit reaches zero, the current flowing through the electric circuit is cut off.

[0074] A time T is set in the controller 6. In the third embodiment, the time T is a preset time. The current value at the time when the time T has elapsed since the current has decreased below the overcurrent threshold value i2 is measured by the overcurrent detection circuit 200. In the third embodiment, the current value at the time when the time T has elapsed since the current has decreased below i2 is defined as c2.

[0075] dI / dt can be approximated as in the following equation (7) using c2, time T, and the overcurrent threshold value i2. Equation (7) can be substituted into equation (4), which is the equation for t2<t<t3 when the semiconductor element 101 is in the off state: dI / dt=(c2-i2) / T (7)

[0076] The controller 6 calculates the value of resistance R and the value of inductance L by solving a simultaneous equation that combines the above equation (2), which is an equation for t1 < t < t2 when the semiconductor element 101 is in the on state, and equation (4), which is an equation for t2 < t < t3 when the semiconductor element 101 is in the off state.

[0077] The semiconductor circuit breaker 1 can estimate the resistance value and the inductance value of the electric circuit even when the semiconductor element 101 is not repeatedly turned on and off as described in the third embodiment. According to the third embodiment, the semiconductor circuit breaker 1 has the effect of being able to easily distinguish between a short circuit state and an overload state, similar to the first embodiment.

[0078] Next, a hardware configuration for realizing the controller 6 according to the first to third embodiments will be described. The controller 6 is realized by a processing circuit. The processing circuit may be a circuit in which a processor executes software, or may be a dedicated circuit.

[0079] When the processing circuit is realized by software, the processing circuit is, for example, a control circuit 60 shown in FIG. 13. FIG. 13 is a diagram showing an example configuration of the control circuit 60 according to the first to third embodiments. The control circuit 60 includes an input unit 61, a processor 62, a memory 63, and an output unit 64. The input unit 61 is an interface circuit that receives data input from outside the control circuit 60 and provides the data to the processor 62. The output unit 64 is an interface circuit that sends data from the processor 62 or the memory 63 to outside the control circuit 60.

[0080] The processor 62 is a CPU (Central Processing Unit). The processor 62 may be a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor). The memory 63 may be, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, or a DVD (Digital Versatile Disc).

[0081] 13 shows an example of hardware in which the functions of the controller 6 are realized by a general-purpose processor 62 and memory 63, but the functions of the controller 6 may also be realized by a dedicated hardware circuit. Fig. 14 is a diagram showing an example of the configuration of a dedicated hardware circuit 65 according to the first to third embodiments.

[0082] The dedicated hardware circuit 65 includes an input unit 61, an output unit 64, and a processing circuit 66. The processing circuit 66 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The controller 6 may be realized by the processing circuit 66 for each function, or the functions of the controller 6 may be realized collectively by the processing circuit 66. The controller 6 may also be realized by combining the control circuit 60 and the hardware circuit 65.

[0083] The configurations shown in the above embodiments are examples of the contents of the present disclosure. The configurations of each embodiment can be combined with other known technologies. The configurations of each embodiment can also be combined as appropriate. Part of the configuration of each embodiment can be omitted or modified without departing from the gist of the present disclosure.

[0084] 1 semiconductor circuit breaker, 2 transformer, 3 distribution line, 4 load, 5 circuit breaker, 6 controller, 7 fault point, 10 power transmission system, 11 power source, 12, 31, 41 resistance, 13, 32, 42 inductance, 60 control circuit, 61 input section, 62 processor, 63 memory, 64 output section, 65 hardware circuit, 66 processing circuit, 100, 100A interrupting module, 101 semiconductor element, 102 diode, 103 nonlinear element, 104 gate power supply, 105 shunt resistor, 106 disconnecting switch, 107 resistive element, 108 switch, 111, 112, 113, 211, 212, 213 terminal, 200 overcurrent detection circuit.

Claims

1. A semiconductor circuit breaker comprising: a breaking module having a semiconductor element and a current limiting element that reduces the current flowing in an electric circuit connecting a power source and a load, wherein the breaking module energizes the electric circuit when the semiconductor element is on and interrupts the current in the electric circuit by switching the semiconductor element from on to off; and a controller that controls the breaking module and estimates at least one of the resistance value and the inductance value of the electric circuit using features extracted from one or more of the power supply voltage of the electric circuit, the element characteristics of the current limiting element, and the current waveform of the electric circuit.

2. The semiconductor circuit breaker of claim 1, characterized in that the characteristic quantities include: a value of the power supply voltage; a value of the voltage generated by the current limiting element; a delay time value which is a preset time; a first current value which is the current value of the current flowing through the electric circuit at a first time which is the time after the delay time has elapsed from the time when the value of the current flowing through the electric circuit exceeds an overcurrent threshold which is a criterion for determining an overcurrent; and a second current value which is the current value of the current flowing through the electric circuit at a second time which is the time after the delay time has elapsed from the time when the value of the current flowing through the electric circuit falls below the overcurrent threshold.

3. The semiconductor circuit breaker of claim 2, characterized in that the first current value is a maximum value of the current waveform after the time when the value of the current flowing through the electric circuit exceeds the overcurrent threshold, and the second current value is a minimum value of the current waveform after the first time.

4. A semiconductor circuit breaker as claimed in claim 2 or 3, characterized in that at the first time, the current path is switched from the semiconductor element to the current limiting element by switching the current flow through the semiconductor element from on to off, and at the second time, the current path is switched from the current limiting element to the semiconductor element by switching the current flow through the semiconductor element from off to on.

5. The semiconductor circuit breaker according to any one of claims 1 to 4, characterized in that the controller estimates a resistance value of the electric circuit and an inductance value of the electric circuit, and determines whether the electric circuit is in a short-circuit state or an overload state based on the estimated resistance value and the estimated inductance value.

6. The semiconductor circuit breaker according to claim 5, characterized in that the controller determines whether the electric circuit is in a short-circuit state or an overload state based on the current value of the current flowing through the electric circuit, the estimated resistance value, and the estimated inductance value.

7. The semiconductor circuit breaker according to claim 5 or 6, characterized in that the controller, when determining that the electric circuit is in a short-circuit state, sends a control command to the circuit breaker module, thereby causing the circuit breaker module to cut off the current in the electric circuit.

8. A semiconductor circuit breaker as claimed in any one of claims 1 to 7, characterized in that the current limiting element is connected in parallel to the semiconductor element.

9. The semiconductor circuit breaker according to any one of claims 1 to 8, characterized in that the current limiting element is a varistor or a Zener diode.

10. A semiconductor circuit breaker as claimed in any one of claims 1 to 8, characterized in that the current limiting element is a resistive element.

11. The semiconductor circuit breaker according to claim 10, further comprising a switch connected in series with the resistive element.

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