Patent Application
20160006368
The present invention relates to a power converter that includes plural semiconductor switching elements, and outputs plural voltage levels, and further relates to a technology that enables the power converter to continue its power conversion operation even when some of the semiconductor switching elements fail.
Power converters such as an inverter and a converter include semiconductor switching elements such as power MOSFETs (metal oxide semiconductor field effect transistors), IGBTs (insulated gate bipolar transistors), GTOs (gate turn off thyristors), and the like. Such power converters can perform various power conversions such as an AC/DC conversion to convert one type of power into other types of power by controlling the on-off operations of those semiconductor switching elements. Therefore, power converters can be used for various applications in which one type of power is converted into other types of power. For example, they are used in, for example, a 50 Hz/60 Hz frequency conversion station of an AC power transmission network in an electric power system, an AC/DC conversion station where an AC power transmission network and a DC power transmission network are connected to each other, a wind power generation system and a solar power generation system whose generated power outputs vary according to natural conditions, and the like.
Since, the failure of a power converter used in an electric power system leads to a blackout, it is required that the power converter should continue its power conversion operation even when some of components included in the power converter fail. In addition, in a wind power generation system or a solar power generation system, since a power generation stoppage owing to the failure of the system influences the profit and loss of the power generation business, it is important to minimize the time period of the power generation stoppage and to improve the capacity utilization ratio of the system. In the case where the installation location of a power generation system cannot be easily accessed, for example, in the case of on the ocean or in a mountainous area, it is especially important that the power generation system can continue its operation even if some power converters fail.
A technology that enables a power converter to continue its operation even in the case of such a failure is disclosed, for example, in Patent Literature 1. The Patent Literature discloses a technology in which a power converter is configured in such a way that the power converter includes at least two phase modules, each of which includes single-phase power conversion modules connected serially in large numbers, and if a single-phase power conversion module included in one phase module fails, the output voltage of a single-phase power conversion module that is included in the other normal phase module of the at least two phase modules and that corresponds to the failed single-phase power conversion module is controlled to be set zero so that the power conversion is continued.
Patent Literature 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-509483
However, according to the technology disclosed in Patent Literature 1, in the power converter including the phase modules having single-phase power conversion modules connected in multiple series, it is required that the output voltages of single-phase power conversion modules that are included in the normal phase modules and that correspond to the failed power conversion module should be controlled to be set zero, therefore the maximum value of the available output voltage is reduced. If the power converter has a comparably high output voltage, the number of single-phase power conversion modules connected in multiple series is large, therefore when a few single-phase power modules included in one phase module fail, even if the output voltages of other normal corresponding phase modules are controlled to be set zero, the maximum value of the available output voltage is not reduced very much. Meanwhile, in the case where a system having a comparatively small output voltage such as a wind power generation system or a solar power generation system includes single-phase power conversion modules connected in multiple series, because the required number of single-phase power conversion modules is small, the maximum value of the available output voltage at the time of failure is largely reduced, so that it becomes necessary for the power converter to be operated in a reduced conversion power mode.
On the other hand, in the case where the number of single-phase power conversion modules, which have low output voltages and are connected in multiple series, is increased in order to decrease the reduction of the maximum value of the available output voltage at the time of failure small, the required number of semiconductor switching elements becomes, which causes the number of total parts to increase greatly.
Further, in the case of a power converter that includes phase modules having semiconductor switching elements connected in multiple parallel, in order not to disturb the switching operations of normal semiconductor switching elements connected in parallel to a failed semiconductor switching element, it is necessary to electrically disconnect the failed semiconductor switching element from the relevant multiple parallel circuit. This causes the maximum value of the conductible current to be reduced, so that it becomes necessary for the power converter to be operated in a reduced conversion power mode.
As described above, in the case where the power converter is configured with single-phase power conversion modules connected in multiple series and semiconductor switching elements connected in multiple parallel in order for the power converter to continue its power conversion operation at the time when a semiconductor switching element fails, the redundancy of the number of parts and the operation of the power converter in a reduced output power mode at the time of failure are unavoidable. A power converter with a comparably low output voltage is greatly influenced and the reduction of its output power becomes obvious.
The present invention is achieved with the abovementioned problems in mind, and one of the objects of the present invention is to provide a power converter that outputs plural voltage levels and is capable of continuing a power conversion operation without reducing its output power even when some of semiconductor switching elements fail.
In order to solve the abovementioned problem, in a power converter according to the present invention, plural semiconductor switching units, each including an on-off switchable semiconductor switching element and a rectifying element connected to the semiconductor switching element in antiparallel, are connected, when a DC voltage is applied to the power converter, the DC voltage is divided into plural different voltage levels, parts having the plural different voltage levels and connection portions where the semiconductor switching units are connected to each other are electrically connected to each other, and the plural different voltage levels are output using the DC voltage by switching the semiconductor switching elements on and off. Any one of the semiconductor switching elements becomes conductive when it fails. The power converter further includes open/close units disposed between the parts having the plural different voltage levels and the connection portions where the semiconductor switching units, which are to be connected to the parts having the different voltage levels, are connected to each other, when an excess current flows through any one of open/close units, the open/close unit opens a current path between the part having the corresponding voltage level and the connection portion where the corresponding semiconductor switching units are connected to each other, the open/close states of the open/close units are detected, and when any one of the open/close units is in an open state, the voltage to which the open/close unit is connected is not output, thereby the number of output voltage levels is reduced.
According to the present invention, a power converter outputting plural voltage levels and capable of continuing its power conversion operation without reducing its output power even when some of semiconductor switching circuits fail can be provided.
Hereinafter, embodiments preferable for a power converter according to the present invention to be materialized will be described in detail with reference to the accompanying drawings. In addition, the same reference signs will be assigned to components common throughout the respective drawings, and duplicate explanations will be omitted. The followings are only explanatory embodiments, and the embodiments of the present invention are not limited to the following concrete embodiments.
a) is a diagram showing the main circuit configuration and control device for one phase unit according to a first embodiment in a diode clamp type power converter, which outputs five different voltage levels, according to a first embodiment. Hereinafter, this type of converter will be abbreviated to a five-level converter, and the same type of converter that outputs X voltage levels will be abbreviated to an X-level converter.
As shown in
Vo is the central voltage level in this five-level converter. The higher voltage level side of the capacitor C−1 is connected to V0, and the voltage level of the lower voltage level side becomes V−1 as a result of the voltage division. The higher voltage level side of the capacitor C−2 is connected to V−1, and the lower voltage level side is connected to the minimum voltage level point V−2 . The diode elements D1 and D′1 are disposed in such a way that the rectification directions of both diode elements D1 and D′1 coincide with each other in a parallel circuit connected between the connection point of S1 and S2 and the connection point of S′1 and S′2, and the connection point between the diode elements D1 and D′1, the voltage level point V1 obtained by the voltage division is connected and the breaking circuit unit B1 is disposed on the connection route. Furthermore, the diode elements D0 and D′0 are disposed in such a way that the rectification directions of both diode elements D0 and D′0 coincide with each other in a parallel circuit connected between the connection point of S2 and S3 and the connection point of S′2 and S′3, the connection point between the diode elements D0and D′0 and the voltage level point V0 obtained by the voltage division is connected, and the breaking circuit unit B0 is disposed on the connection route. In addition, the diode elements D−1 and D′−1 are disposed in such a way that the rectification directions of both diode elements D−1 and D′−1 coincide with each other in a parallel circuit connected between the connection portion of S3 and S4 and the connection portion of S′3 and S′4, the connection point between the diode elements D−1 and D′−1 and the voltage level point V−1 obtained by the voltage division is connected, and the breaking circuit unit B−1 is disposed on the connection route. The five-level converter includes plural phase units that are configured in the above way and disposed in parallel with a DC section. Furthermore, although semiconductor switching elements are depicted by IGBT element symbols in
In addition, each of the semiconductor switching units S includes a mechanism that brings a semiconductor switching element into a conductive state when the semiconductor switching element fails. This mechanism may be, for example, a pressure contact type semiconductor switching element that goes into a short-conductive state when it fails, a semiconductor switching element having a normally-on characteristic that makes itself in a conductive state with no external control signal applied thereto, any semiconductor switching element having a short circuit such as an electromagnetic contact device connected in parallel, or the like. Any semiconductor switching unit may be used as one of the semiconductor switching units as long as it has a mechanism that goes into a short-circuited state when it fails.
Furthermore, each of the breaking circuit units B that cuts off its electric connectivity when an excess current flows through itself may be, for example, a fuse whose conductive route melts down owing to heat energy generated by an excess current; a current breaking device that cuts off its conductive route after detecting an excess current by a current sensor or the like; a mechanism that realizes an excess current breaking function using a combination of a semiconductor switching element and a current sensor for detecting an excess current; a route breaking device that can be operated by an external command signal, or the like. Needless to say, a mechanism other than the above-described devices can be used as long as it is a mechanism having a function of breaking its conductive route (without receiving an external command).
Furthermore, as for the disposal positions of the breaking circuit units B, the breaking circuit units B can be disposed at any positions of the routes on electric circuits in such a way that the breaking circuit units B can electrically break the conductive routes that electrically connect the different voltage level points V1, V0, V−1 divided by the capacitors and the respective connection points of semiconductor switching units S1 to S′4. For example, it is all right that the breaking circuit unit B1 exerts a function to simultaneously break the conductive route between the connection point of the semiconductor switching units S1 and S2 and the voltage level V1 and the conductive route between the connection point of the semiconductor switching units S′1 and S′2 and the voltage level V1, therefore it is conceivable that a combination of mechanisms disposed on plural positions of the circuit is assigned to the breaking circuit unit B1.
A voltage command V* output from a command value calculation device 4, a carrier wave signal SW output from a carrier generation device 3, and binary signals SigB1, SigB0, SigB−1 showing the open/close states of the breaking circuit units 2 (B) are input into a semiconductor switching unit controller 1 (SCU). Although it is assumed that an open state and a close state will be respectively depicted by 0 and 1 in the embodiments in this specification, it goes without saying that the way to express an open state and a close state is not limited to this notation. The semiconductor switching unit controller 1 outputs rectangular wave type control signals SigS1 to SigS′4 for respectively controlling the on-off operations of the semiconductor switching units S1 to S′4. The rectangular wave type control signals output from the semiconductor switching units S are respectively activated as four pairs of (SigS1, SigS′1), (SigS2, SigS′2), (SigS3, SigS′3), and (SigS4, SigS′4), so that two semiconductor switching units included in each of four pairs of the semiconductor switching units (S1, S′1), (S2, S′2), (S3, S′3), and (S4, S′4) are controlled not to go into a conductive state simultaneously. The above mechanism for preventing the simultaneous conductive state from occurring is generally referred to as dead-time control, and the compensation of output voltages performed by the introduction of the dead-time is referred to as dead-time compensation. Since the dead-time processing does not contribute to the development of the advantageous effects of the present invention, the explanation about this processing will be omitted.
Hereinafter, the case where the respective semiconductor switching units S1 to S′4 are short-circuitedly failed will be explained. As described above, each of the semiconductor switching units S has a function to go into a conductive state when it fails, and becomes always on when it is short-circuitedly failed.
In the case where the semiconductor switching unit S1 fails short-circuitedly, if the rectangular wave type control signals SigS1 to SigS′4 for outputting the voltage V1 are provided, these rectangular wave type control signals (SigS1, SigS2, SigS3, SigS4, SigS′f1 SigS′2, SigS′3, SigS′4) become (0, 1, 1, 1, 1, 0, 0, 0). However, since the semiconductor switching unit S1 is always on, the semiconductor switching units S1 to S4, and S′1 are conductive. Therefore, electric energy stored in the capacitor C2 is discharged as a short-circuit current through a route shown in
In the case where the semiconductor switching unit S2 fails short-circuitedly, if the rectangular wave type control signals SigS1 to SigS′4 for outputting the voltage V0 are provided, these rectangular wave type control signals (SigS1, SigS2, SigS3, SigS4, SigS′1, SigS′2, SigS′3, SigS′4) become (0, 0, 1, 1, 1, 1, 0, 0). However, since the semiconductor switching unit S2 is always on, the semiconductor switching units S2 to S4, and S′1 and S′2 are conductive. Therefore, electric energy stored in the capacitor C1 is discharged as a short-circuit current through a route shown in
In the case where the semiconductor switching unit S3 fails short-circuitedly, if the rectangular wave type control signals SigS1 to SigS′4 for outputting the voltage V−1 are provided, these rectangular wave type control signals (SigS1, SigS2, SigS3, SigS4, SigS′1, SigS′2, SigS′3, SigS′4) become (0, 0, 0, 1, 1, 1, 1, 0). However, since the semiconductor switching unit S3 is always on, the semiconductor switching units S3 and S4, and S′1 to S′3 are conductive. Therefore, electric energy stored in the capacitor C−1 is discharged as a short-circuit current through a route shown in
In the case where the semiconductor switching unit S4 fails short-circuitedly, if the rectangular wave type control signals SigS1 to SigS′4 for outputting the Voltage−2 are provided, these rectangular wave type control signals (SigS1, SigS2, SigS3, SigS4, SigS′1, SigS′2, SigS′3, SigS′4) become (0, 0, 0, 0, 1, 1, 1, 1). However, since the semiconductor switching unit S4 is always on, the semiconductor switching units S4 and S′1 to S′4 are conductive. Therefore, electric energy stored in the capacitor C−2 is discharged as a short-circuit current through a route shown in
In the case where the semiconductor switching unit S′1 fails short-circuitedly, if the rectangular wave type control signals SigS1 to SigS′4 for outputting the voltage V2 are provided, these rectangular wave type control signals (SigS1, SigS2, SigS3, SigS4, SigS′1, SigS′2, SigS′3, SigS′4) become (1, 1, 1, 1, 0, 0, 0, 0). However, since the semiconductor switching unit S′4 is always on, the semiconductor switching units S1 to S4 and S′1 are conductive. Therefore, electric energy stored in the capacitor C2 is discharged as a short-circuit current through a route shown in
In the case where the semiconductor switching unit S′2 fails short-circuitedly, if the rectangular wave type control signals SigS1 to SigS′4 for outputting the voltage V1 are provided, these rectangular wave type control signals (SigS1, SigS2, SigS3, SigS4, SigS′1, SigS′2, SigS′3, SigS′4) become (0, 1, 1, 1, 1, 0, 0, 0). However, since the semiconductor switching unit S′2 is always on, the semiconductor switching units S2 to S4, and S′1 and S′2 are conductive. Therefore, electric energy stored in the capacitor C1 is discharged as a short-circuit current through a route shown in
In the case where the semiconductor switching unit S′3 fails short-circuitedly, if the rectangular wave type control signals SigS1 to SigS′4 for outputting the voltage V0 are provided, these rectangular wave type control signals (SigS1, SigS2, SigS3, SigS4, SigS′1, SigS′2, SigS′0, SigS′4) become (0, 0, 1, 1, 1, 1, 0, 0). However, since the semiconductor switching unit S′3 is always on, the semiconductor switching units S3 and S4, and S′1 to S′3 are conductive. Therefore, electric energy stored in the capacitor C−1 is discharged as a short-circuit current through a route shown in
In the case where the semiconductor switching unit S′4 fails short-circuitedly, if the rectangular wave type control signals SigS1 to SigS′4 for outputting the voltage−1 are provided, these rectangular wave type control signals (SigS1, SigS2, SigS3, SigS4, SigS′1, SigS′2, SigS′3, SigS′4) become (0, 0, 0, 1, 1, 1, 1, 0). However, since the semiconductor switching unit S′4 is always on, the semiconductor switching units S4 and S′1 to S′4 are conductive. Therefore, electric energy stored in the capacitor C−2 is discharged as a short-circuit current through a route shown in
As described above, if any one of the semiconductor switching units S1 to S′4 is short-circuitedly failed, a short-circuit current is cut off by any one of the breaking circuit units B1, B0, and B−1. Furthermore, in order to surely cut off the short-circuit current, the power conversion operation can be stopped for a short time as needed. It becomes possible to use a disconnecting unit, which does not have a current breaking function but has a disconnecting function, instead of a breaking circuit unit, by allowing the power conversion operation to be stopped for a short time.
The semiconductor switching unit controller 1 for the five-level converter will be explained in the case where the breaking circuit unit B1 is activated as shown in
Subsequently, in a similar way to the normal state, the rectangular wave type control signals SigS1 to SigS′4, which respectively control the on-off operations of the semiconductor switching units S1 to S′4, are calculated by comparing the calculated four carrier wave signals SWSigS1,S′1, SWSigS2,S′2, SWSigS3,S′3, and SWSigS4,S′4 with the input voltage command V* respectively. The calculated rectangular wave type control signals SigS1 to SigS′4 are output to the semiconductor switching units S1 to S′4. The normal semiconductor switching units are turned on and off by the control signals SigS1 to SigS′4. Then a stepped AC voltage Vac including four different voltage levels V2, V0, V−1, and V−2 can be output within the permissible voltage range for withstand voltages of the switching units S and the diode elements D. As a result, the five-level converter can be activated equivalently as a four-level converter, and even when any one of the semiconductor switching units S1 to S′4 fails, the power conversion operation can be continued. In addition, because the maximum and minimum values of the output voltage level are not changed in comparison with those in the normal state of the five-level converter, the output power is also unchanged.
The semiconductor switching unit controller for the five-level converter in the case where the breaking circuit unit B0 is activated as shown in
Although not shown, in the case where the breaking circuit unit B−1 is activated, the carrier wave signal SW is expanded, shrunk, and shifted in the voltage level interval V0-V−2 with the voltage level V−1, which cannot be output, and the carrier wave signals SWSigS3,S′3 and SWSigS4,S′4 are calculated in a similar way to the above-described cases. Subsequently, in a similar way to the normal state, the rectangular wave type control signals SigS1 to SigS′4, which respectively control the on-off operations of the semiconductor switching units S1 to S′4, are calculated by comparing the calculated four carrier wave signals SWSigS1,S′1, SWSigS2,S′2, SWSigS3,S′3, and SWSigS4,S′4 with the input voltage command V* respectively. The calculated rectangular wave type control signals SigS1 to SigS′4 are output to the semiconductor switching units S1 to S′4. The normal semiconductor switching units are turned on and off by the control signals SigS1 to SigS′4. Then a stepped AC voltage Vac including four different voltage levels V2, V1, V0, and V−2 can be output within the permissible voltage range for withstand voltages of the switching units S and the diode elements D. As a result, the five-level converter can be activated equivalently as a four-level converter, and even when any one of the semiconductor switching units S1 to S′4 fails, the power conversion operation can be continued. In addition, since the maximum and minimum values of the output voltage level are not changed in comparison with those in the normal state of the five-level converter, the output power is also unchanged.
Even in the case where, after any one of the breaking circuit units B is activated, another operates, the behavior of the five-level converter is similar to the above-described cases, and the five-level converter can continue its power conversion operation as a three-level converter within the permissible voltage range for withstand voltages of the switching units S and the diode elements D. Detailed explanations about this case will be omitted.
The above-described behaviors of the five-level converter can be generalized. More specifically, an X-level converter, which outputs plural voltage levels, according to the present invention can continue its power conversion operation without reducing its output power by reducing the number of output levels into X-1 to 3, 2 sequentially in accordance with the operations of the breaking circuit units B within the permissible voltage range for withstand voltages of the switching units and the diode elements D included in the X-level converter even if some semiconductor switching elements fail.
A second embodiment will be described with reference to
The breaking circuit units B described in the first embodiment can be used as the breaking circuit units B for this embodiment. Furthermore, the breaking circuit units Bare not limited to the breaking circuit units B described in the first embodiment, and any other mechanisms can also be used as long as they have functions to open or close their conductive routes using command signals after detecting excess currents. However, if the breaking circuit units B comprise disconnecting devices, since the breaking circuit units B do not have a function of current breaking when they are in a current conducting state, when one of the breaking circuit units B detects an excess current, it outputs an excess current detection signal and the power conversion operation is stopped for a short time as needed. Subsequently, after the short-circuit current is attenuated, the corresponding disconnecting device is operated, and the power conversion operation is restarted in accordance with a behaviors similar to that performed in the first embodiment. In this case, it is necessary that this embodiment should include a mechanism for protecting capacitors C from the short-circuit current as needed.
Although short-circuit currents owing to the short-circuit failures of the respective semiconductor switching units S flow through the same routes as those described in the first embodiment, the open/close operations of the breaking circuit units B in this embodiment are performed in a similar way to the open/close operations performed in the first embodiment by controlling the open/close operations of the breaking circuit units B using the open/close command signals CmdB1, CmdB0, and CmdB−1 output from the breaking circuit unit controller 12 (BCU). It is also possible in the configuration of this embodiment that a five-level converter according to this embodiment can continue the power conversion operation as an equivalently lower-level converter within the permissible voltage range for withstand voltages of the switching units S and the diode elements D. Since the behavior of the power converter of this embodiment is the same as that of the first embodiment, a detailed explanation thereof will be omitted.
Because the breaking circuit units B according to this embodiment can be controlled using the open/close command signals CmdB1, CmdB0, and CmdB−1 output from the breaking circuit unit controller, the power converter of this embodiment can not only continue the operation of power conversion described in the first embodiment, but also can maintain the rectangular shape of an output voltage Vac after the short-circuit failure of one of the semiconductor switching units S in an up-down symmetrical waveform regardless of which of the semiconductor switching units fails.
For example, in the case where the breaking circuit unit B1 outputs the excess current signal OCB1 owing to the short circuit failure of one of the semiconductor switching units S, the breaking circuit unit controller 12 (BCU) outputs a breaking operation command not only to the breaking circuit unit B1, but also to the breaking circuit unit B−1, which connects a divided voltage level V−1 and another of the semiconductor switching units S in order to limit the output of the voltage level V−1 that is electrically symmetrical to a voltage level V1 whose electric connection to the connection point of the one of the semiconductor switching units S is broken by the breaking circuit unit B1. In other words, not only the open signal CmdB1, but also the open signal CmdB−1 is output. In addition, the breaking circuit unit controller 12 (BCU) outputs the open/close state signals (SigB1, SigB0, SigB−1)=(0, 1, 0) to the semiconductor switching unit controller. Meanwhile, in the case where the breaking circuit unit B−1 outputs the excess current signal OCB−1, not only the open signal CmdB−1, but also the open signal CmdB is output. Furthermore, the breaking circuit unit controller 12 (BCU) outputs the open/close state signals (SigB1, SigB0, SigB−1)=(0, 1, 0) to the semiconductor switching unit controller.
The main circuit configuration of the five-level converter becomes equivalent to the main circuit configuration of a three-level converter shown in
Furthermore, for example, in the case where the breaking circuit unit B0 outputs the excess current signal OCB0 owing to one of the short circuit failure of semiconductor switching units S, the breaking circuit unit controller 12 (BCU) outputs only a release signal CmdB0 if there is no voltage level electrically symmetrical to the voltage level V0 whose electric connection to the connection point of the one of the semiconductor switching units S is broken by the breaking operation of the breaking circuit unit B0, and further the breaking circuit controller outputs the open/close state signals (SigB1, SigB0, SigB−1)=(1, 0, 1) to the semiconductor switching unit controller. In a power converter is an odd number-level converter, it does not have a voltage level that is electrically symmetrical to the central voltage level. The main circuit configuration of the five-level converter is activated as a four-level converter shown in
As described above, the breaking circuit unit controller selectively outputs an open signal to one of the breaking circuit units B in accordance with a voltage level where an excess current is detected, which enables the output voltage Vac to remain in a symmetrically rectangular waveform even at the time of failure. Therefore, the middle voltage level variation of average output per unit time of the output voltage Vac generated by the continuous running of the power converter can be minimized.
In addition, in a power converter that converts multiphase AC power using plural phase units for a three-phase AC or the like, by issuing an open command signal CmdB for a voltage level, which is equal to the voltage level of a failed phase unit, to normal phase units other than the failed phase unit via breaking circuit unit controllers of the respective normal phases, an advantageous effect of minimizing a negative-phase-sequence component and a zero-phase-sequence component of a multiphase AC voltage generated by the continuous running of the power converter can be obtained, and the amount of unnecessary power , which is supplied to a load connected to the power converter, can be reduced, wherein, for example, in the case where the normal phase sequence of a three-phase AC is a sequence of U, V, and W phases, and a normal output is an output with this phase sequence, while the negative phase sequence means that it is a phase sequence in which any two of the U, V, and W phases are not in the right order, and a zero phase component is, for example, an average output voltage of instantaneous output voltages of a three-phase AC, and a zero phase means a state in which a DC component is added to a three-phase AC component.
Although diode clamp type X-level converters have been described in the above embodiments, it goes without saying that the present invention can be applied to other types of converters. For example, in an active clamp type X-level converter shown in
Alternatively, as shown in
SCU: Semiconductor Switching Unit Controller
BCU: Breaking Circuit Unit Controller
S: Semiconductor Switching Unit
D: Diode, Free Wheeling Rectifying Element
C: Capacitor
B: Breaking Circuit Unit
V: Voltage
SW: Carrier Wave Signal
SigS: Semiconductor Switching Unit Control Signal
SigB: Breaking Circuit Unit State Signal
OCB: Breaking Circuit Unit Excess Current Signal
CmdB: Breaking Circuit Unit Control Signal
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/054072 | 2/20/2013 | WO | 00 |
