CN104885363A - Semiconductor switch arrangement - Google Patents

Abstract

A semiconductor switching device comprising, for each current phase, a first semiconductor switch (2a), a second semiconductor switch (2b), a first diode (3a), a second diode (3b), with Means for measuring voltage from input and output lines of said semiconductor switch, and means (8) for measuring current arranged in series with said semiconductor switch. Additionally, the device comprises a control element (14) configured to switch on the semiconductor switching device at a point of zero voltage and to switch off the semiconductor switch at a point of zero current.

Description

semiconductor switchgear

Background technique

The present invention relates to methods and apparatus for switching circuits.

One of the problems associated with conventional mechanical switches is that arcing tends to occur between the contact surfaces when turned off, which causes wear on the switch.

Contents of the invention

Therefore, the purpose of this solution is to provide a new method and a device for implementing the method. The objects of the invention are achieved by a method and a device which are characterized by what is stated in the independent claims. Preferred embodiments of the invention are disclosed in the dependent claims.

The solution is based on the idea of switching the circuit stepwise from on to off using the properties of a pair of semiconductor switches for each current phase and a diode connected in series with each semiconductor switch, wherein each diode can is the external or internal diode of another semiconductor switch.

An advantageous feature of the method and device of this solution is that a zero-voltage connection and a zero-current disconnection to the circuit can be arranged, which makes it possible to provide a solution that does not generate arcs when switched off.

Description of drawings

The solution will be described in more detail below by means of a preferred embodiment with reference to the attached (additional) drawings, in which:

Figures 1a and 1b are schematic diagrams of semiconductor switching devices for 1-phase AC circuits;

Figure 2 schematically illustrates a method for switching current in a circuit;

Figure 3 schematically illustrates another method for switching current in a circuit;

Figure 4 is a schematic graph showing phase voltage and phase current versus time during a turn-on event in a circuit comprising a semiconductor switching device;

Figure 5 is a schematic graph showing phase voltage and phase current versus time during a turn-off event in a circuit comprising a semiconductor switching device;

Fig. 6 schematically shows a semiconductor switching device according to an embodiment;

Fig. 7 schematically shows a semiconductor switching device of another embodiment;

Fig. 8 schematically shows a semiconductor switching device for a 3-phase AC circuit according to a block diagram;

FIG. 9 shows schematically according to a block diagram the switching on of a 3-phase semiconductor switching device at zero voltage;

Fig. 10 shows schematically according to a block diagram the switching off of a 3-phase semiconductor switching device in the case of zero current;

FIG. 11 schematically illustrates overcurrent shutdown logic for an embodiment including an active crowbar in block diagram form;

Fig. 12 schematically shows an embodiment of a semiconductor switching device for a 3-phase AC circuit comprising series isolating switches; and

Figure 13 schematically illustrates a method for shutting down a circuit in an overcurrent event.

Detailed ways

In the figures, similar structural and/or functional parts and components are denoted by the same reference numerals.

Figures 1a and 1b are schematic diagrams of a semiconductor switching device for a 1-phase AC circuit. The embodiment shown in Figure 1 a comprises a semiconductor switching device 1 connected to a 1-phase alternating current (AC) circuit. The semiconductor switching device of FIG. 1a comprises a first semiconductor switch 2a and a second semiconductor switch 2b connected in parallel. The first diode 3a is connected in series with the first semiconductor switch 2a, and the second diode 3b is connected in series with the second semiconductor switch 2b, such that the forward bias of the first diode and the second diode The direction is opposite to the forward bias direction of the inner diodes of the respective first and second semiconductor switches connected in series with said diodes. Also shown in the figure are 1-phase AC source 4, input resistor 5a, input inductor 5b, load current 10, load resistor 6a and load inductor. Additionally, the device of FIG. 1 a also comprises means for measuring voltage 7 and means for measuring current 8 arranged in series with said semiconductor switch for measuring current. Preferably, the semiconductor switching device further comprises an overvoltage protection element 9 for absorbing inductive energy generated by shutting down the circuit in an overcurrent event. Thus, the overvoltage protection element 9 may be used to limit the voltage across the semiconductor switch to prevent the semiconductor switch from breaking. The semiconductor switching device of FIG. 1 a can be used to control switching on a circuit at a point of zero voltage and switching off a circuit at a point of zero current.

Switching on at the point of zero voltage can be achieved by the method according to FIG. 2 , wherein the polarity of the phase voltages is detected 201 in response to a command to switch on the circuit. The polarity of the phase voltages can be detected by the means 7 for measuring voltages. A semiconductor switch connected in series with the reverse biased diode can then be turned 202 into a conductive state. This means that if the voltage is positive, the second semiconductor switch 2b is turned on to the conductive state, and if the voltage is negative, the first semiconductor switch 2a is turned on to the conductive state. At this time, no current flows in the main circuit because the corresponding diode 3b or diode 3a connected in series with the semiconductor switch 2b, 2a which is switched on to the conductive state is reverse biased, thus preventing the current flow in the circuit flow. When the polarity of the phase voltage is changed, the current starts to flow in the main circuit through the semiconductor switch in the conducting state and the corresponding diode connected in the forward direction after the polarity change of the phase current, which in the conducting state The lower semiconductor switch is the first semiconductor switch 2a or the second semiconductor switch 2b depending on the original polarity of the voltage, and the corresponding diode is the corresponding first diode 3a or the second diode depending on the original polarity of the voltage Tube 3b. Simultaneously, the other semiconductor switch, which is still turned off during the originally detected voltage polarity and in the positive direction The connected diodes are connected in series with the semiconductor switches. Therefore, current flows in the main circuit during both current polarities. Furthermore, a second polarity change of the phase voltages can be detected by the means 7 for measuring voltages. Thus, the main circuit is turned on at zero voltage. This is an advantageous way of switching on a circuit, since current spikes can be avoided and there are no voltage surges associated with switching on events, so that for example electromagnetic interference can be avoided.

An example of using such a device and switching on a circuit according to such a method is shown in FIG. 4 , in which the variation of the phase voltage 12 and phase current 11 with respect to time is shown. In the example, the switching device receives a command to turn on the circuit at the instant of time _t0 , and since the phase voltage is negative, the first semiconductor switch 2a is turned on into a conducting state. When the phase voltage 12 changes polarity at the instant of time _t1 , the phase current 11 starts to flow in the main circuit, and at the same instant the second semiconductor switch 2b is also turned on to a conducting state.

Switching off at the zero current point can be achieved by the method according to Fig. 3, wherein the polarity of the phase voltage and the polarity of the phase current are detected 301 in response to a command to switch off the circuit. The polarity of the phase voltages and the change in polarity of the phase voltages can be detected by the means for measuring voltage 7 and the polarity of the phase currents and the change in polarity of the phase currents can be detected by means for measuring the current 8 . The semiconductor switches 2a, 2b connected in series with the reverse biased diodes 3a, 3b are turned off 302 into a non-conductive state in response to the phase voltage being of the same polarity as the phase current being of the same polarity. This means that if both the voltage and current are positive, the second semiconductor switch 2b is turned off into a non-conductive state, and if both the voltage and current are negative, the first semiconductor switch 2a is turned off into non-conductive state. If the polarity of the phase voltage and the phase current are not the same, ie one is negative and the other is positive, no action is taken until the same polarity of the phase voltage and phase current is detected. Thus, when the phase current is changing its direction, the phase current no longer has a current path due to the reverse bias of the diode 3a, 3b connected in series with the semiconductor switch 2a, 2b still in the conducting state, on the other hand , another semiconductor switch in the non-conducting state also prevents current flow. Then, the semiconductor switch still in the conducting state is turned off 303 to a non-conducting state after a time substantially equal to an AC half cycle has elapsed since the other semiconductor switch was turned off in step 302 . In this way it can be ensured that the polarity of the voltage and the polarity of the current are opposite to the direction in which the semiconductor switch conducts the current. The phase voltages should also be monitored to ensure that the current is no longer switched on due to the phase difference between the phase current and the phase voltage. This is a beneficial way to turn off a circuit because a turn-off event at zero current prevents voltage spikes that could cause electromagnetic interference to the device itself or to other devices. Additionally, it may not be necessary to use a fast turn off of the mechanical switch, which can extend the life of the mechanical switch.

An example of using such a device and switching off a circuit according to such a method is shown in FIG. 5 , where the variation of the phase voltage 12 and phase current 11 with respect to time is shown. In the example, the switching device receives a command to turn off the circuit at time _t0 , at which point the phase voltage 12 and the phase current 11 are both negative, first turning off the first semiconductor switch 2a to a non-conductive state . When the phase current 11 changes its direction at the instant of time t ₁ , the current no longer has a current path and the current in the main circuit is switched off. When a time substantially equal to the AC half cycle has elapsed at the instant of time _t2 , the second semiconductor switch 2b is also turned off into a non-conductive state to prevent the current from returning during the next half cycle. In other words, in FIG. 5 , basically t ₂ -t ₀ =T/2. This makes the device and method independent of the frequency of the circuit to which the device is connected, thereby enabling the same device to be used in circuits of any frequency such as 50 Hz, 60 Hz or 400 Hz.

Figure 1b shows a simpler and more cost-effective semiconductor switching device 1 . In this embodiment, the first semiconductor switch 2a and the second semiconductor switch 2b are connected in series, so that the internal diode (so-called body diode) of the first semiconductor switch 2a replaces the second diode 3b, and the second semiconductor switch The inner diode of 2b (the so-called body diode) replaces the first diode 3a. Apart from that, the connections can be similar and such an embodiment can implement the methods shown in Figures 2 and 3 in the same way. This embodiment can be used where the specified maximum forward current for the internal diode of the semiconductor switch is sufficient for the application in question.

FIG. 6 shows an embodiment of a semiconductor switching device, wherein the semiconductor switching device also includes a main switch 13 . The semiconductor switching device 1 can eg be similar in all other respects to the semiconductor switching device shown in FIGS. 1a and 1b and the method of FIGS. 2 and 3 can be implemented using the semiconductor switching device 1 . In FIG. 6, the semiconductor switches 2a, 2b and diodes 3a, 3b are similar to the semiconductor switches 2a, 2b and diodes 3a, 3b of FIG. 1a. The main switch 13 may comprise a mechanical switch, such as an ultra-fast bistable mechanical switch which is particularly beneficial in short circuit events, although different types of mechanical switches may be used in different embodiments. In such an embodiment, the main switch 13 may be in a non-conductive state at the moment the command to close the circuit is received. The semiconductor switches 2a, 2b can then be switched on according to the method explained in conjunction with FIG. 2 to switch on the current in the circuit. Then, when both the semiconductor switches 2a, 2b are in the conductive state, the main switch 13 can be turned on to be in the conductive state. The current path can then be commutated from the semiconductor switch 2a, 2b branch to the main switch 13 branch due to lower on-state losses. Then, the semiconductor switches 2a, 2b can be turned off in a non-conductive state.

When a command to turn off the circuit is received, firstly the semiconductor switches 2a, 2b can be turned on to be in a conducting state. Then, the main switch 13 can be turned off to a non-conductive state. Thereafter, for example, as described in connection with FIG. 3 , the main circuit may be turned off to prevent current flow.

Fig. 7 shows another embodiment which may otherwise be similar to the embodiment of Fig. 6, while the semiconductor switches 2a, 2b and the diodes 3a, 3b part are similar to those of Fig. 1b .

Fig. 8 shows a semiconductor switching device for a 3-phase AC circuit as a block diagram. In a 3-phase AC application of the semiconductor switching device 1 described above, the semiconductor switching device according to Fig. 1 a, Fig. 1 b, Fig. 6 or 7 and the method according to Fig. 2 and/or Fig. 3 can be applied individually for each phase. Fig. 8 also shows a control element 14 and some other components and units that may be used in controlling the semiconductor switching device. The same control element 14 may be configured for use in both 1-phase and 3-phase applications.

The main switch 13 of the 3-phase switch may comprise a mechanical switch, eg an ultra-fast bistable mechanical switch. The semiconductor switching device 1 may also comprise: semiconductor switches 2a, 2b optionally including diodes 3a, 3b, an overvoltage protection element 9, means for measuring voltage 7 of the phase lines and means for measuring current 8, said A device 8 for measuring current is arranged in series with the semiconductor switch for measuring the current 8 of the phase conductor. In different embodiments, the semiconductor switching device 1 may also include at least one of the following: a graphical user interface 15, a control element 14 (for example, a programmable integrated circuit (IC), such as a field programmable gate array (FPGA) , microcontroller (MCU) or digital signal processor (DSP)), active crowbar (active crowbar) 17, current measurement circuit 16 of active crowbar, including means 19 for determining the maximum current value and for The overcurrent protection circuit 18 of the device 20 for determining the maximum current rate, the main switch drive circuit 21 of the phase line, the semiconductor switch drive circuit 22 of the phase line and the drive circuit 23 of the active crowbar.

Each phase of the 3-phase semiconductor switching device comprises a main switch 13 connected in parallel with the semiconductor switches 2 a , 2 b and the overvoltage protection element 9 . Preferably, such a semiconductor switch is fully controllable such that it can be switched on and off at will. The semiconductor switches 2a, 2b may comprise insulated gate bipolar transistors (IGBTs), gate turn-off thyristors (GTOs) or integrated gate commutated thyristors (IGCTs).

According to an embodiment, a graphical user interface 15 may be connected to the control element 14 . The graphical user interface may be configured to: receive input from a user to set a set point for the 3-phase semiconductor switching device; provide commands to the 3-phase semiconductor switching device; and have status information and measurements from the 3-phase semiconductor switching device.

According to an embodiment, the device 7 for measuring the voltage of the phase line can be connected to the control element 14 . The voltage can be measured from the input and output of the switching means 13, 2a, 2b according to each phase. The control element 14 can control the switching function of the 3-phase switch on the basis of the voltage measurement obtained by the device 7 for measuring voltage. The control element 14 may also use the voltage measurements to control the normal shutdown function of the 3-phase switch.

According to an embodiment, the device 8 for measuring the current of the phase line can be connected to the control element 14 and to the overcurrent protection circuit 18 . The device 8 for measuring the current in each phase can be connected in series with the switching element 13, 2a, 2b between the switching element 13, 2a, 2b and an optional active crowbar circuit. The control element 14 can control the normal shut-off function of the switch on the basis of current measurements obtained by means 8 of the phase conductors for measuring current. An overcurrent protection circuit 18 connected to the means 8 for measuring current of the phase line and connected to the control element 14 can process the current measurement obtained by the means 8 for measuring current of the phase line, and the overcurrent protection circuit 18 At least one of the following types of information may be provided to the control element: a maximum value of the absolute value of the phase current and a maximum value of the current rate of change of the phase current. The control element 14 can use its internal comparator to compare the determined maximum value with a reference value. The control element 14 may then detect an overcurrent event in case the determined maximum value is greater than the reference value. For example, the reference value can be set in the graphical user interface 15 .

According to an embodiment, the current measuring device of the active crowbar is connected to the control element 14 . The active crowbar current measuring device is connected in series with the active crowbar semiconductor switch to measure the current through the active crowbar semiconductor switch. The control element 14 controls the semiconductor switches of the active crowbar on the basis of the current measurement.

According to an embodiment, the drive circuit 22 of the semiconductor switches of the phases can be connected between the control element 14 and the semiconductor switches 2a, 2b of the phases. The control element may be configured to generate a control signal to the drive circuit 22 of the semiconductor switch of the phase to switch the semiconductor switch on or off.

According to an embodiment, the phase main switch drive circuit 21 may be connected between the control element 14 and the phase main switch 13 . The control element 14 may be configured to generate a control signal to the main switch drive circuit 21 of the phase to move the contacts, in some embodiments mechanical contacts, of the main switch 13 to an open position or a closed position. Location.

According to an embodiment, the semiconductor switching device comprises a so-called active crowbar 17 which can be used to give a current path for the inductive load current when switching off in an overcurrent event. The driving circuit 23 of the active crowbar can be connected between the control element 14 and the active crowbar 17 . The control element 14 may then be configured to generate a control signal to the drive circuit 23 of the active crowbar that switches the semiconductor switch of the active crowbar on or off. The benefit of such an embodiment is that the energy stored in the load during such a switch-off event can be absorbed in the resistive part of the load instead of having the load energy only absorbed in the overvoltage protection element 9 . This can prolong the lifetime of the overvoltage protection element.

Thus, in each phase line, the semiconductor switches may comprise two semiconductor switches 2a, 2b. Some examples of different types of suitable semiconductor switches are discussed above in connection with other embodiments. For each semiconductor switch there may also be a diode 3a, 3b connected in series. The two pairs of diode semiconductor switches in one phase may be connected in antiparallel such that when the semiconductor switches are switched on, a positive current, i.e. a current from source to load, flows through the pair comprising the first semiconductor switch 2a and the first diode 3a, and the negative current, ie the current from the load to the source, flows through another diode-semiconductor pair comprising the second semiconductor switch 2b and the second diode 3b. An overvoltage protection element 9 such as that described in connection with the other embodiments can be used as overvoltage protection device. These overvoltage protection elements 9 may be connected in parallel with the main switch 13 and the semiconductor switches 2a, 2b to limit the voltage across the switches and absorb the inductive energy of the main circuit when the current is interrupted in an overcurrent event.

According to an embodiment, the semiconductor switches 2a, 2b may each be individually controlled by a semiconductor switch drive circuit 22 comprising a driver such as an optocoupler drive circuit. In different embodiments, the parallel main switches 13 may be controlled by a main switch drive circuit 21 comprising a driver, eg an optocoupler driver. Using optocouplers is beneficial because optocouplers provide good voltage isolation between the primary and secondary sides and low propagation delay. The voltage can be measured from both sides of the switching elements 2a, 2b, 3a, 3b, 13—from the source side (U_nS) and the load side (U_nL)—by means of the device 7 for measuring voltage. The current in the phase conductor is measured using means 8 for measuring current, such as a current sensor with good accuracy, wide frequency bandwidth and good galvanic isolation between the primary and secondary sides. For example, a closed loop Hall effect current sensor may be suitable. The overcurrent protection circuit may include analog electronics.

According to an embodiment, switching on a 3-phase semiconductor switching device can be done at zero voltage without electromagnetic interference according to a method substantially similar to that described in connection with FIG. 2 , but naturally this switching must be made for each Phase and independent. Zero voltage switching can be done using the semiconductor switches 2a, 2b, and the main switch can be kept off as long as all semiconductor switches are switched on, as described in connection with eg FIGS. 6 and 7 . The semiconductor switches can be turned on in each phase based on the polarity of the voltage across them, referred to as U_nS and U_nL in FIG. 9 , where S refers to source, L refers to load, and n refers to each voltage phase. If the voltage across the switches is positive, the second semiconductor switch 2b of the phase is turned on (indicated by S2, S4, S6 in the block diagram of Figure 9), and if the voltage across the switches is negative, the second semiconductor switch 2b of the phase is turned on. A semiconductor switch 2a is switched on (indicated by S1, S3, S5 in the block diagram of FIG. 9). After switching on a semiconductor switch, the diodes 3a, 3b connected in series with the semiconductor switch are then reverse biased. Hence, no current flows in the phase conductor until the polarity of the voltage across the switching means changes. When current flows through one semiconductor switch, the other semiconductor switch of the phase is also turned on. In a 3-phase system, current in the main circuit starts to flow after one phase is switched on if the neutral wire is connected, and after both phases are switched on if the neutral wire is not connected. The current in the circuit starts to flow. After all phase conductors are switched on, the selectable main switches 13 of all phases are switched on. The current is commutated to the branch of the main switch due to the higher on-state voltage of the semiconductor switch. These principles are shown in Figure 9 in terms of a block diagram representing the normal-on logic for a 3-phase application.

According to an embodiment, switching off a 3-phase semiconductor switching device can be done at zero current, thereby preventing arcing between mechanical contacts when switching off an inductive load. Zero current turn-off can be accomplished using semiconductor switches according to the same principles as described above in connection with eg FIG. 3 . To achieve this effect, the phase current needs to be commutated to the semiconductor switch first by turning it on and then turning off the ultra-fast switch. In the event of a switch-off, a zero-current switch-off using semiconductor switches can be achieved using the means for measuring current 8 and the means for measuring voltage 7 of the phase conductors. As explained in connection with eg FIG. 3 , the semiconductor switches are turned off independently for each phase based on the polarity of the phase voltage and the polarity of the phase current. If the current in one phase is positive, ie the current is directed from the source to the load, the second semiconductor switch 2b (denoted S2, S4, S6 in the block diagram of Fig. 10) where the negative current flows is turned off. If the current in one phase is negative, the first semiconductor switch 2a (denoted S1, S3, S5 in the block diagram of Fig. 10) in which the positive current flows is turned off. In FIG. 10 , phase currents are indicated by I_n, where n refers to each phase, and phase voltages are indicated by U_n, where n refers to each phase. Now, after a semiconductor switch of a phase line has been switched off, the current flow in this phase is not interrupted until the polarity of the phase current changes. The other semiconductor switch, which is still in the conducting state, can then also be turned off after a delay of the AC half cycle (called 1/2 grid cycle or half grid cycle in FIG. 10 ). Due to the possible phase difference between current and voltage, the turn-off event must be done when the polarity of the phase voltage is the same as that of the phase current. Otherwise, the current can be switched on again. In 3-phase AC applications, the current in the main circuit is switched off after all phases are switched off if the neutral is connected, and after both phases are switched off if the neutral is not connected current in the main circuit. These principles are shown in Figure 10 in terms of a block diagram representing the normal shutdown logic for a 3-phase application.

Shutdown in an overcurrent event can be achieved by the method according to FIG. 13 . According to an embodiment, the overcurrent protection of the 3-phase AC switch can be done based on the current value and/or based on the rate of change of the current. According to an embodiment, the control element 14 may detect 131 an overcurrent event based on the current value determined by the means 8 for measuring current. The control element may detect an overcurrent event in response to a measurement of current in one phase being greater than a predetermined current limit. In some embodiments, the current limit can be set in a user interface, such as a graphical user interface. The user interface may be, for example, the user interface described in connection with other implementations.

According to an embodiment, the control element 14 may detect an overcurrent event based on the rate of change of current. The control element may detect 131 an overcurrent event in response to the measured value of the rate of change of current in one phase being greater than a current rate of change limit. In some embodiments, the current rate of change limit can be set in a user interface, such as a graphical user interface. The user interface may be, for example, the user interface described in connection with other implementations. The advantage of overcurrent protection based on the rate of current change is that the abnormal rate of current change indicating an overcurrent can be detected at a lower overcurrent value, which is much before the abnormal rate of current change is at a dangerous level from a system perspective, which reduces the of stress. Thus, this detection method is safer than conventional overcurrent protection based on current level, because the overcurrent does not reach the same high value by the time of shutdown. In other embodiments, both the current value and the rate of change of current may be used for detecting an overcurrent event.

According to an embodiment, after detecting an overcurrent event, the control element 14 may generate 132 an ON signal to the semiconductor switches 2a, 2b and an OFF signal to the main switch 13 to commutate current to the semiconductor switches 2a, 2b. After a predetermined time, when the insulation gap between the contacts of the main switch 13 is sufficient, the control element 14 may generate 133 a switch-off signal to the semiconductor switches 2a, 2b to interrupt the current flow in the main circuit. A sufficient insulation gap is when the breakdown voltage of the insulation gap is greater than the protection level, ie the clamping voltage, of the overvoltage protection element 9 connected in parallel to the switching elements 2 a , 2 b , 13 . After the semiconductor switches 2a, 2b are switched off, the voltage across the switching components starts to increase due to the inductor in the main circuit. When the voltage reaches a protection level, the overvoltage protection element forms a low resistance shunt across the switching element. The energy stored in the inductor of the main circuit is then absorbed 134 in the overvoltage protection element 9 . In different embodiments, the isolation gap of the main switch 13 may include air or other isolation substances or a combination thereof.

The lifetime of the overvoltage protection element 9 generally depends on the energy absorbed in the overvoltage protection element. The larger the transient, the shorter the overall lifetime of the overvoltage protection components will be. Thus, a significant benefit of rate-of-current-based overcurrent protection is that it detects overcurrent events faster than current value-based overcurrent protection, resulting in much smaller overcurrent transients. Thus, this will further increase the lifetime of the overvoltage protection element.

According to an embodiment, a so-called active crowbar circuit can be used in systems where the load inductor is relatively large to further increase the lifetime of the overvoltage protection element 9 . Figure 11 is a block diagram illustrating the overcurrent shutdown logic in such an embodiment with an active crowbar as described above connected. Thus, such an active crowbar circuit can be connected to the load side. An overcurrent event may be detected 111 in a manner similar to that described in connection with other embodiments. The semiconductor switching device 1 can be switched off in a manner similar to that described in steps 132 and 133 in connection with FIG. However, in an embodiment comprising such an active crowbar 17, after generating the switch-off signal 115 to the semiconductor switches 2a, 2b of the phase line, the control element 14 may then generate a connection to the semiconductor switches of the active crowbar. Signal 116. Thus, the inductive load current can be commutated by an active crowbar that absorbs the load energy in the resistive part of the load rather than in the overvoltage protection element. In embodiments where the load is an active load and stores both inductive and mechanical energy, the mechanical energy may maintain or even increase the current through the active crowbar, which would eventually destroy the semiconductor. In such an embodiment, an active crowbar current measurement circuit 16 may be provided to prevent this by measuring the current through the semiconductor switch of the active crowbar 17, which current measurement circuit 16 may include, for example, a current sensor. Furthermore, the current measurement circuit 16 of the active crowbar may be connected to a control element 14 which may generate a shutdown signal to the semiconductor switch of the active crowbar 17 in response to a current value greater than a predetermined crowbar current limit. Thereafter, the remainder of the load energy can be absorbed in the overvoltage protection element 9 .

According to another embodiment, an optocoupler driving circuit 23 for driving an active crowbar may be used to detect a current value greater than a predetermined crowbar current limit value, wherein the optocoupler driving circuit 23 includes an active crowbar The integrated desaturation detection of the semiconductor switch of 17, and the optocoupler drive circuit 23 further gives fault status feedback to the control element 14. Such drivers may include, for example, IGBT drivers that detect an overcurrent event when the voltage between the collector and emitter of the IGBT is higher than a defined value. According to an embodiment, the driver may automatically turn off the semiconductor switch of the active crowbar and give fault status feedback to the control element 14 in response to detecting desaturation of the semiconductor switch of the active crowbar. After receiving the fault signal, the control element can then generate a reset signal to the driver for activating the driver and can switch on the semiconductor switch of the active crowbar again if required. The benefit of this embodiment is that, for example, by using this type of optocoupler drive circuit, the current measurement circuit 16 of the active crowbar can be omitted, but the optocoupler drive circuit and current Measuring circuit 16 both.

Fig. 12 schematically shows an embodiment of a semiconductor switching device for a 3-phase AC circuit, which may eg be similar to the embodiment shown in Fig. 8, but comprising a series isolating switch 24 for each phase. For example, such switches can be used for galvanic isolation of switchgear to ensure electrical safety during maintenance work. According to certain embodiments, such a series disconnect switch 24 may be provided in any of the embodiments described above.

It will be obvious to a person skilled in the art that as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims (15)

1. for a semiconductor switching device for commutation circuit, wherein, described switchgear comprises mutually for each electric current:

First semiconductor switch and the second semiconductor switch, described first semiconductor switch and described second semiconductor switch can be controlled to arbitrarily turn on and off;

First diode and the second diode, described first diode and described second diode are for controlling available current path;

For from the input line of described semiconductor switch and the device of output line measuring voltage;

For measuring the device of electric current, itself and described semiconductor switch in series arrange the electric current measuring phase line; And

Control element, its order being configured to turn on and off in response to the described circuit of connection by controlling described semiconductor switch in response to voltage measurements and current measurement result is connected described semiconductor switching device and under zero-current point, is turned off described semiconductor switch in response to the order turning off described circuit under no-voltage point.

2. semiconductor switching device according to claim 1, wherein, described first semiconductor switch and described second semiconductor switch of described semiconductor switching device are connected in series, and described first diode and described second diode comprise the internal body diodes of described semiconductor switch and be used to control described available current path.

3. semiconductor switching device according to claim 1, wherein, described first semiconductor switch of described semiconductor switching device is connected in parallel with described second semiconductor switch, described first diode and described first semiconductor switch are connected in series, and described second diode and described second semiconductor switch are connected in series, make the forward bias direction of described first diode and described second diode to described Diode series the forward bias direction of internal body diodes of the first corresponding semiconductor switch of being connected and the second semiconductor switch contrary.

4. semiconductor switching device according to any one of claim 1 to 3, wherein, described semiconductor switching device also comprises main switch, and described main switch and described semiconductor switch are connected to realize lower on-state loss in the on-state in parallel.

5. semiconductor switching device according to any one of claim 1 to 4, wherein, described circuit is 3 phase AC circuit.

6. semiconductor switching device according to any one of claim 1 to 4, wherein, described circuit is 1 phase AC circuit.

7. semiconductor switching device according to any one of claim 1 to 6, wherein, described semiconductor switching device also comprises overvoltage protection element mutually for each.

8. semiconductor switching device according to any one of claim 1 to 7, wherein, described semiconductor switching device also comprises active crow bar.

9. semiconductor switching device according to any one of claim 1 to 8, wherein, described semiconductor switching device also comprises the series connection isolating switch for electric current isolation mutually for each electric current.

10. semiconductor switching device according to any one of claim 1 to 9, wherein, described control element is configured to:

The polarity of phase voltage is detected in response to the order of connecting described circuit;

Make with back-biased described Diode series the described semiconductor switch that is connected connect as conducting state; And

Change in polarity in response to described phase voltage makes to connect as conducting state with the described semiconductor switch be connected during original detected polarity of voltage forward biased described Diode series.

11. semiconductor switching device according to any one of claim 1 to 9, wherein, described control element is configured to:

The polarity of phase voltage and the polarity of phase current is detected in response to the order turning off described circuit;

Polarity in response to described phase voltage is identical with the polarity of described phase current make with back-biased described Diode series the semiconductor switch that is connected turn off; And

From turn off to have passed through second half conductor switch be substantially equal to the AC semi-cyclic time after still described semiconductor switch is in the on-state turned off as nonconducting state.

12. semiconductor switching device according to any one of claim 7 to 9, wherein, described control element is configured to:

One of at least carry out detection of excessive current event in response in following situation: one mutually in the measured value of electric current be greater than scheduled current limit value; And one mutually in the measured value of current changing rate be greater than current changing rate limit value;

Generate the connection signal of extremely described semiconductor switch and commutate to described semiconductor switch to the cut-off signals of described main switch to make electric current;

The cut-off signals of extremely described semiconductor switch is generated to interrupt the electric current in main circuit after the scheduled time;

Make to be stored in energy absorption in the inductor of main circuit after electric current in main circuit is interrupted in described overvoltage protection element.

13. 1 kinds of methods for the electric current in commutation circuit, described circuit comprises semiconductor switching device, described semiconductor switching device comprises the first semiconductor switch, the second semiconductor switch, the first diode, the second diode, for from the input line of described semiconductor switch and the device of output line measuring voltage and the device for measuring electric current, described method comprises:

The polarity of phase voltage is detected in response to the order of connecting described circuit;

Make with back-biased Diode series the semiconductor switch that is connected connect as conducting state; And

Change in polarity in response to described phase voltage makes to connect as conducting state with the semiconductor switch be connected during original detected polarity of voltage forward biased described Diode series.

14. methods according to claim 13, described method also comprises:

The polarity of phase voltage and the polarity of phase current is detected in response to the order turning off described circuit;

Polarity in response to described phase voltage is identical with the polarity of described phase current make with back-biased described Diode series the semiconductor switch that is connected turn off; And

From turn off to have passed through second half conductor switch be substantially equal to the AC semi-cyclic time after still described semiconductor switch is in the on-state turned off as nonconducting state.

15. methods according to claim 13 or 14, wherein, described semiconductor switch also comprises overvoltage protection element, and described method also comprises:

One of at least carry out detection of excessive current event in response in following situation: one mutually in the measured value of electric current be greater than scheduled current limit value; And one mutually in the measured value of current changing rate be greater than current changing rate limit value;

Generate the connection signal of extremely described semiconductor switch and commutate to described semiconductor switch to the cut-off signals of main switch to make electric current;

The cut-off signals of extremely described semiconductor switch is generated to interrupt the electric current in main circuit after the scheduled time;

Make to be stored in energy absorption in the inductor of main circuit after electric current in main circuit is interrupted in described overvoltage protection element.