JP4571957B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device capable of supplying large power exceeding a rating for a short time.

  In recent years, electronic devices that are sensitive to fluctuations in power supply voltage, such as precision electronic devices equipped with personal computers and precision motors, have been frequently used. For this reason, there is an increasing demand for countermeasures against instantaneous voltage drop (hereinafter abbreviated as “instantaneous drop”), which is a phenomenon in which the power supply voltage drops significantly for a short time of several seconds or less. As a device for instantaneous voltage drop countermeasures, there is a stable power supply device that can supply a large amount of power for a short time only when the voltage drops, and the demand for this device is increasing. In addition, the conventional power leveling device, peak cut device, frequency fluctuation suppressing device, voltage stabilizing device, flicker countermeasure device, and other various power stable supply devices are also short for measures against instantaneous voltage drop. It is required to add a capacity to supply a large amount of power (hereinafter referred to as “instantaneous large power supply capacity”) although it is time. Furthermore, an instantaneously large power supply capability is required even in an electric heating device or a lighting device using a large number of large bulbs. That is, since the temperature of the coil heater is low at the start of the operation of the electric heating device or the lighting device, the resistance is lower than that during the steady operation. Therefore, a large current flows and the power conversion device is required to have an instantaneous large power supply capability.

  In addition, in induction heating equipment for metal heat treatment, etc., in order to heat-treat metal parts quickly under high-precision temperature control, the heating furnace in a low temperature state at the start of operation is rapidly brought to a predetermined high temperature or rapidly It is necessary to make the temperature low. For this reason, compared with the case where high temperature is maintained in a steady operation state, large electric power is required at the time of an operation start. The electric power when it is necessary to supply a large amount of power for such a short time is called “instantaneous large electric power”, and the device for supplying the instantaneous large electric power is called “instantaneous large electric power supply device”. Motors and the like also require a large amount of electric power to start rotating from a stationary state at the start of operation, and a power conversion device for motors is required to have an instantaneous large electric power supply capability. In the case of an electric vehicle or the like, it is necessary to drive the motor with a larger electric power than in normal driving, although it is a short time, when starting or when escaping when a tire enters a muddy state. Thus, there are various types of load devices that require instantaneous high power. The conventional technology will be described below by taking as an example a stable power supply device that is a conventional instantaneous large power supply device. The time when loads such as the load leveling device, the stable power supply device such as the peak cut device, the electric heating device, the lighting device, and the motor device are operating in a steady state is hereinafter referred to as “normal time”.

  FIG. 10 is a block diagram of a power supply system having a conventional stable power supply apparatus 101 using a redox flow battery as the secondary battery 108. In the figure, a system bus 102 is connected to a power system 100 of a substation 130 via a transformer 120. The stable power supply apparatus 101 is connected to the system bus 102 via a switch 103. For example, important loads 104 and 105 are connected to the system bus 102 via respective switches 114 and 115. The important loads 104 and 105 are important facilities for large customers who need a particularly stable power supply such as semiconductor manufacturing factories and precision machining factories. A general load 110 is also connected to the system bus 102 via switches 109 and 111. The stable power supply apparatus 101 includes a transformer 106 that also serves as an interconnection reactor, a converter 107 that converts AC power into DC power, or vice versa, and a large-capacity secondary battery 108 (redox flow battery). I have. This stable power supply device 101 functions as a peak cut device and a load leveling device in normal times, but instantaneous voltage drop to prevent the critical loads 104 and 105 from shutting down at the time of a momentary drop due to a lightning accident or the like Also works as a preventive measure device.

  Hereinafter, the function of the stable power supply apparatus 101 will be described in detail. In the “steady state” in which the power supply and demand of the power supply system connecting the substation 130, the important loads 104 and 105, and the general load 110 is balanced, the switch 103 and the transformer from the system bus 102 AC power is supplied to the stable power supply apparatus 101 through 106. The AC power is converted into DC power by the converter 107 and stored in the secondary battery 108. When the power consumption of the important load 104 or 105 is greatly increased and the power supplied to the loads 104 and 105 temporarily exceeds the capacity of the substation 130, the detection circuit 8 having the voltage detector 10 The state is detected. The detection output of the detection circuit 8 is given to the control circuit 9. The control circuit 9 controls the converter 107 to convert the DC power generated by the discharge of the secondary battery 108 into the AC power by the converter 107, and supplies the surplus effective power to the system bus 102 to stabilize the supply and demand. Let This function is called “peak cut” because the stable power supply apparatus 101 can supply the excess power to be supplied from the substation 130 to the system bus 102 instead, and the peak of the power supplied to the system bus 102 can be cut. It is out.

  When the capacity of the secondary battery 108 of the stable power supply apparatus 101 is increased so that electric power that can be supplied for a long time can be stored, it can be used as a load leveling apparatus. That is, the secondary battery 108 is charged with constant power during a low demand time zone at night (typically about 8 hours), and is constant time (typically about 8 hours) during high demand hours during the day. Electric power is supplied from the secondary battery 108 with constant power. Thereby, electric power more than the electric power which can be supplied of the substation 130 can be supplied in a high demand time zone. The stable power supply device for this application is called a “load leveling device” because it leveles a large gap between day and night power demand.

  When lightning arrives at the power system 100 and a voltage drop occurs in the system voltage, the voltage detector 10 detects the voltage drop. In order to prevent the operation of the important loads 104 and 105 from being stopped due to a voltage drop, it is necessary to immediately restore the system voltage before the voltage drop. For this purpose, the stable power supply apparatus 101 controls the converter 107 by the control circuit 9 and supplies reactive power and active power from the secondary battery 108 to the important loads 104 and 105 via the converter 107 and the system bus 102. To maintain a stable power supply. When the power supplied from the secondary battery 108 is insufficient, the switch 109 is opened to disconnect the general load 110 having a low importance level, and at least the important loads 104 and 105 are supplied with a desired power to supply the important loads 104 and 105. We are trying to prevent the outage. As soon as the voltage drop recovers, the converter 107 returns to the normal operating state and supplies power from the substation 130.

  In a conventional stable power supply apparatus, at the time of peak cut or load leveling, for example, the former is about 500 kW and the latter is about 2 MW for a relatively long time (for example, the former is about 1 hour, the latter is about 8 hours). It is required to supply. When a lightning strike occurs due to lightning during peak cut or load leveling operation, a power of 1 MW to several MW is added for a relatively short time (for example, 2 seconds) to recover the lowered voltage. It is necessary to supply.

  Distribution lines to which loads that require instantaneous high power at the time of starting an electric heating device, a lighting device using a light bulb, a motor, etc. are normally capable of supplying instantaneous high power. Secondary batteries that supply power to heaters, light bulbs, and motors for automobiles, and fuel cells for electric cars also have instantaneous high power supply capability. In addition, secondary batteries such as redox flow batteries, sodium-sulfur batteries, and lead batteries used for stable power supply can supply a much larger current than the rated current for a short time from a few seconds to a few minutes. have. In other words, if it is several seconds to several minutes, a current several times the rated current that can be supplied at normal times can be supplied. If this capability is utilized when instantaneous high power is required, instantaneous high power can be supplied without increasing the rated capacity of the secondary battery to a capacity corresponding to the instantaneous high power. However, the silicon (Si) semiconductor element used as the switching element of the converter 107 which is the power conversion apparatus of the conventional stable power supply apparatus does not have the ability to control the power exceeding several times the rating. . Therefore, it is necessary to set the rated power of converter 107 to a value substantially equal to the instantaneous high power. Therefore, in normal times, the power is used at a fraction of the rated power.

At the start of operation of an electric heating device and a lighting device using a light bulb, the time until the temperature of the coil heater rises to a steady state, or the time until the motor starts and reaches a predetermined rotational state Compared to time, this is a very short time. Further, in the stable power supply apparatus, the instantaneous drop due to the arrival of lightning does not occur so frequently and is about 20 times a year at most. The duration of the instantaneous drop due to lightning is several seconds even in the case of multiple lightning. In rare cases, small animals such as snakes and birds may be caught on power transmission lines, or trees may come into contact with each other, causing short circuits and ground faults. In such a case, a relatively long “instantaneous power outage” exceeding several minutes may occur. However, in order to deal with such a momentary power drop during a short time or a momentary power failure, providing a power converter such as a large converter with a power rating several times that of normal power There was a problem that not only the large power supply apparatus was large and the equipment cost was high, but also the maintenance cost was high.
JP 2002-84683 A JP-A-11-32438 International publication number WO 98/43301 International Publication Number WO00 / 22679 JP 2000-252475 A

  The present invention uses a semiconductor element in which the operation mode can be selectively changed between the normal time and the time when instantaneous high power is required by the control by the control electrode, thereby having a power rating corresponding to the power required for the normal time. It is an object of the present invention to provide a power conversion device that can supply power that greatly exceeds normal power when the device is started, instantaneously low, or when an instantaneous power failure occurs.

In order to solve the above problems, a power conversion device of the present invention is
A wide gap composite function semiconductor element having a composite function for selecting whether to operate as a unipolar semiconductor element or a bipolar semiconductor element by control by a control electrode,
Using the wide gap composite function semiconductor element as a switching element, performing at least one of an operation of converting AC to DC and outputting, or an operation of converting DC to AC and outputting , or DC to DC While performing the conversion and output operation,
The wide gap composite function semiconductor element normally operates as the unipolar semiconductor element, and operates as the bipolar semiconductor element when instantaneous high power is required .

  According to the power conversion device having the above configuration, when the gate voltage is lower than the built-in voltage of the gate junction, it functions as a unipolar semiconductor element, and when the gate voltage is higher than the built-in voltage of the gate junction, it functions as a bipolar semiconductor element. A gap composite function semiconductor element is used as a switching element. For example, by operating a wide gap composite function semiconductor element as a unipolar semiconductor element during normal operation and as a bipolar semiconductor element when instantaneous high power is required, the power conversion device normally operates at rated power while instantaneously operating. When large power is supplied, it operates with power significantly exceeding the rated power. Since this large power supply time is short, the semiconductor element is not destroyed. Therefore, even though the power conversion device has a power rating corresponding to the power required during normal operation, it is possible to supply electric power that greatly exceeds normal power when the device is started, during a sag, or when an instantaneous power failure occurs.

Also , during normal operation with power below the rated power, the wide gap composite function semiconductor element is operated as a unipolar semiconductor element, and operation starts to start various devices (loads) that require instantaneous power loss or instantaneous high power. At times (hereinafter referred to as “device start-up”), by operating the wide gap composite function semiconductor device as a bipolar semiconductor device, the power converter operates at rated power during normal operation. When supplying a large amount of instantaneous power, it will operate at a power significantly exceeding the rated power.

  In one embodiment, the wide gap composite functional semiconductor element is a charge injection junction field effect transistor (CIJFET) using silicon carbide (SiC) as a base material.

  According to the above embodiment, since the internal resistance of the charge injection junction field effect transistor (CIJFET) using silicon carbide (SiC) as a base material has a positive temperature dependency, an excessive current flows and the element temperature rises. As the internal resistance increases, the current is automatically reduced and temperature rise is suppressed, and thermal runaway does not occur.

  In one embodiment, the wide gap composite functional semiconductor element includes at least one chip or a plurality of chips of a charge injection junction field effect transistor (CIJFET) using the silicon carbide (SiC) as a base material. Are connected in parallel.

  In one embodiment, the wide gap composite function semiconductor element is a charge injection MOS field effect transistor (CIMOSFET) using silicon carbide (SiC) as a base material.

  In one embodiment, the wide gap composite functional semiconductor element is at least one chip or a plurality of chips of a charge injection MOS field effect transistor (CIMOSFET) using the silicon carbide (SiC) as a base material. Are connected in parallel.

  In one embodiment, the wide gap composite function semiconductor element is a semiconductor element having gallium nitride as a base material.

  As described in detail in each of the above embodiments, according to the present invention, a power conversion device such as an inverter is configured using a wide gap composite functional semiconductor element in which either unipolar operation or bipolar operation is selected. When the output is below the rated power, unipolar operation is performed. When instantaneous high power is required, the bipolar operation of the wide gap composite function semiconductor device is performed so that power exceeding the rated power at normal time can be controlled. Thereby, the effect that the size reduction, weight reduction, and cost reduction of a power converter device can be acquired is acquired.

  Embodiments of the present invention will be described below.

  In the instantaneous high power supply device having the power conversion device using the wide gap composite function semiconductor element as a switching element of the present invention, the wide gap composite function semiconductor element is operated as a unipolar semiconductor element in a normal state, and at the time of an instantaneous drop or a load When a large amount of instantaneous power is required, such as at the start of operation of the device (when the device is started), the device is operated as a bipolar semiconductor element. As a result, the power converter normally operates at the rated power and has a low loss. Although the loss increases at the time of a voltage drop or when the apparatus is started, it can be operated with a power significantly exceeding the rated power.

  In particular, wide-gap semiconductor devices based on SiC (silicon carbide), GaN (gallium nitride), diamond, etc. have significantly less loss than semiconductor devices based on Si (silicon) and operate at high temperatures. It has the physical property of being able to. Focusing on this point and investigating the maximum allowable power for a short time that can be controlled by a wide gap semiconductor device, it was destroyed even if a current far exceeding the rated current was passed through the wide gap semiconductor device for a short time of about several seconds. It turns out not to be. In particular, it was confirmed that the wide gap bipolar semiconductor device has an “instantaneous high power operation capability” capable of flowing a large current that greatly exceeds the “instantaneous high current supply capability” of the secondary battery.

  In the power conversion device (converter) according to the present invention, a wide gap composite function semiconductor element that operates as a unipolar semiconductor element during normal operation and operates as a bipolar semiconductor element at the time of start-up that requires instantaneous high power is used as a switching element. Normally, it is operated at a voltage and current within the rating of the wide gap unipolar semiconductor element. At the time of voltage sag or when the device is started, the DC power is discharged several times the normal value due to the instantaneous high current supply capability of the secondary battery, and the wide gap composite function semiconductor element of the converter is operated as a bipolar semiconductor element. Is converted into AC power, and power is supplied to an electric heating device, a lighting device, a motor device, or the like.

  When the voltage of the secondary battery is lower than the voltage of the system bus, the DC output voltage due to the discharge of the secondary battery is boosted by the chopper circuit, converted to AC power by the converter, and output to the system bus. The secondary battery is charged “normally”. At the time of charging the secondary battery, AC power from the system bus is converted into DC power by the converter, stepped down by the chopper circuit, and charged to the secondary battery. The electric power value charged / discharged under normal conditions is within the rating of the converter.

  At the time of a voltage drop or an instantaneous power failure, a current several times the rated current is supplied while maintaining the rated voltage of the secondary battery in accordance with the instantaneous large current supply capability of the secondary battery. That is, DC power that is approximately several times the rated power is supplied from the secondary battery. This DC power is boosted by a chopper circuit, converted to AC power by a converter, and output to the system bus, thereby stabilizing the power supply.

  The converter performs pulse width modulation by performing general known PWM operation type switching control on the switching element of the wide gap composite function semiconductor element. The phase of the output voltage of this pulse width modulation type converter (hereinafter referred to as PWM converter) is advanced from the phase of the voltage of the system bus, and the same power as normal is output to the system bus. Output to the bus is desirable for stable power supply. Since the voltage of the system bus decreases at the time of a sag, the pulse width modulation pulse width is widened to operate the converter. As a result, reactive power several times the normal value is output to the system bus, and the reduced voltage is rapidly returned to the voltage before the instantaneous drop.

  A wide gap composite function semiconductor element using silicon carbide (SiC) or the like as a base material for low power control can be configured using one semiconductor chip. However, it is difficult to construct a wide gap composite function semiconductor element for high power control with a single semiconductor chip. This is because it is difficult to produce a large-area semiconductor chip without any defects because many crystal defects exist in the base material SiC of the wide gap semiconductor element. In particular, it is difficult to manufacture a chip having a large area capable of flowing a large current as in the application of the present invention. If the technology for reducing the crystal defects of SiC is improved, a semiconductor device having a chip with a large area similar to that of Si can be realized. However, at present, a plurality of chips are connected in parallel to allow a large current to flow.

  In a conventional converter using a Si bipolar transistor or Si IGBT provided in a conventional instantaneous high power supply device, the rated capacity of the Si bipolar transistor or Si IGBT is set to a secondary value at the time of an instantaneous drop or start of operation. The capacity must be set to match the normal power supplied from the battery.

  On the other hand, in the instantaneous large power supply device of the present invention, the SiC CIJFET or the SiC CIMOSFET has a composite function, and therefore a converter using this can control a large current several times the rated current. Therefore, even if the converter is set according to the rated current of the wide gap composite function semiconductor element, which is the switching element of the converter, in accordance with the normal current, it can cope with a large current at the time of a sag. Various components constituting the instantaneous high power supply device such as a stable power supply device, for example, a transformer as a reactor, a heat sink of a semiconductor element, a bus bar, and the like can be reduced in size. In addition, since the rated capacity is small, the absolute value of loss is small and the loss can be reduced even with the same conversion efficiency, and a significant cost reduction can be achieved. Large converters for electric power use are required to have high breakdown voltage and high reliability compared to small converters. Moreover, since many protection functions are required, the price is high. For example, in a case where a conventional instantaneous high power supply apparatus requires a 5 MW converter, the present invention requires only 1 MW. For this reason, the cost is almost one fifth that of the conventional one, and a significant cost reduction can be achieved. The effect of cost reduction becomes greater as the instantaneous large power supply apparatus having a larger power capacity.

  A preferred embodiment of the instantaneous high power supply apparatus of the present invention will be described below with reference to FIGS.

<< First Example >>
FIG. 1 shows an instantaneous high power supply device 1 for peak cut using the power conversion device of the first embodiment of the present invention, and an important load 104 from a substation 130 to which the instantaneous high power supply device 1 is connected. , 105 and an instantaneous load 110 are block diagrams of the power supply system. “Peak cut” refers to supplying excess from a power source other than the substation 130 when the power consumption exceeds the power that can be supplied by the substation 130 due to a sudden increase in power demand. Is called “at peak cut”. The state other than the peak cut is referred to as “steady state”. In the figure, a system bus 102 is connected to a power system 100 of a substation 130 via a transformer 120. Particularly important important loads 104 and 105 are connected to the system bus 102 via respective switches 114 and 115. Further, a general load 110 having a lower importance than the important loads 104 and 105 is connected to the system bus 102 via switches 109 and 111. When an abnormality occurs in the system bus 102, the switch 109 first disconnects the general load 110 and preferentially maintains the power supply to the important loads 104 and 105. The instantaneous power supply apparatus 1 of the present invention is connected to the system bus 102 via the switch 6. A control device for operating the switches 6, 109, 111, 114 and 115 is not shown because it is well known in the art.

  The instantaneous high-power supply device 1 includes a secondary battery 2 having a rated voltage of 3.2 kW using a 500 kW rated redox flow battery, a converter 4 as an example of a 500 kW rated power conversion device, and a transformer that also serves as an interconnection reactor. And is connected to a 6.6 kV system bus 102 via a switch 6. The voltage and current of the system bus 102 are detected by the voltage detector 10 and the current detector 11, respectively, and the power supply / demand state is detected by the detection circuit 8 based on the detected voltage and current. A potential transformer (PT) or the like is used for the voltage detector 10. The current detector 11 is a current transformer (CT) or the like, and is provided in the substation 130 to detect the output current of the substation 130. The control circuit 9 receives a control signal output from the mode switching circuit 13 in accordance with a detection output indicating the supply / demand state of the electric power supplied from the detection circuit 8, and applies a corresponding drive signal to the converter 4 to output power. To control. When the voltage of the redox flow battery of the secondary battery 2 is 800 V, a bidirectional chopper circuit 3 is provided between the secondary battery 2 and the converter 4 as shown in FIG. Boost. The secondary battery 2 has a capacity capable of supplying a DC voltage of 800 V and a current of 625 A for about 1 hour. The switching elements of the chopper circuit 3 and the converter 4 are charge injection junction field effect transistors (hereinafter referred to as CIJFETs). The rated voltage of the CIJFET of the chopper circuit 3 is 8 kV and the rated current is 800 A, the rated voltage of the CIJFET of the converter circuit 4 is 8 kV, and the rated current is 400 A. The power capacity of this device is about 450 kW considering the power loss generated in the chopper circuit 3, the converter 4 and the transformer 5.

  When the power consumption of the important loads 104 and 105 increases and temporarily exceeds the output power capacity of the substation 130, the voltage detector 10 and the current detector 11 detect the state, and the instantaneous large power supply device The converter 4 is controlled through the detection circuit 8, the mode switching circuit 13, and the control circuit 9, and the active power corresponding to the excess power can be supplied from the secondary battery 2 to the system bus 102 up to a maximum of about 450 kW. The secondary battery 2 is charged with electric power supplied from the system bus 102 in a steady state in which the supply and demand of electric power between the substation 130 and the important loads 104 and 105 and the general load 110 is balanced.

  The DC output voltage of the secondary battery 2 such as a redox flow battery is, for example, 800 V at the beginning of the usage period, but tends to decrease from 800 V as the usage period becomes longer. Therefore, at the time of peak cut, it is desirable that the output voltage of the secondary battery 2 is boosted by the constant voltage output holding type chopper circuit 3 and the voltage is always kept constant and supplied to the converter 4.

  The converter 4 that converts direct current power into alternating current power or converts alternating current power into direct current power uses SiC-CIJFETs, which are wide gap composite function semiconductor elements having SiC as a base material, as switching elements. Since the converter 4 has a general known circuit configuration, the illustration thereof is omitted. In SiC-CIJFET, it is difficult to increase the current rating due to limitations due to defects in the SiC crystal. Therefore, it is desirable to obtain a desired power rating at a low current rating by increasing the voltage rating. In this case, as shown in FIG. 2, the output voltage 800V of the redox flow battery of the secondary battery 2 is boosted to 3.2 kV by the chopper circuit 3 and DC power of about 3.2 kV and 300 A is supplied to the converter 4. ing. The converter 4 converts this DC power into AC power and applies it to the transformer 5. The transformer 5 boosts the voltage of 3.2 kV to 6.6 kV, outputs it to the system bus 102 via the switch 6, and supplies it to the loads 104, 105 and 110.

  When the instantaneous high power supply device 1 supplies 450 kW peak cut power at the time of peak cut, if a lightning strike occurs in the power system 100, the voltage of the system bus 102 is instantaneously reduced (instantaneous drop). ) Is detected by the voltage detector 10. The instantaneous drop may cause a serious failure such as operation stop on the important loads 104 and 105. Therefore, in order to prevent this, the switch 109 is immediately opened and the general load 110 is disconnected. At the same time, the detection output of the voltage detector 10 is input to the detection circuit 8 in the instantaneous high power supply device 1. The detection circuit 8 generates a command signal for determining the operation mode of the control circuit 9 based on the detection output and applies it to the mode switching circuit 13. The mode switching circuit 13 applies to the control circuit 9 a control signal that determines an operation mode for operating the SiC-CIJFET of the converter 4 as a unipolar semiconductor element or a bipolar semiconductor element. The control circuit 9 inputs a PWM control signal for PWM control of the SiC-CIJFET which is a switching element of the converter 4 to the converter 4 based on the input control signal. The control circuit 9 controls the converter 4 so that the secondary battery 2 outputs a DC power of 2.5 MW corresponding to the instantaneous large current supply capability, for example, at a voltage of 800V. The chopper circuit 3 boosts the 800V DC voltage to 3.2 kV and supplies it to the converter 4. In the converter 4, the gate voltage of the SiC-CIJFET is increased by the control circuit 9, and the SiC-CIJFET is switched from the unipolar operation to the bipolar operation. As a result, the converter 4 outputs active power of 450 kW at a voltage of 1.47 kV and reactive power of 2.78 MVAR (representing a unit of reactive power) at a voltage of about 1.47 kV.

  The voltages of the active power and the reactive power are boosted to 6.6 kV by the transformer 5 and supplied to the system bus 102 to prevent a voltage drop. It is extremely rare that the voltage drop of the system bus 102 due to the lightning strike continues for 0.5 seconds or more. Since the converter 4 is designed so that the instantaneous high power supply device 1 of this embodiment can supply 450 kW of active power and 2.78 MVAR of maximum reactive power for about 6 seconds, it is sufficient as a measure against an instantaneous drop caused by a lightning strike. . In the above example, the converter 4 can convert an instantaneous high power of about 6 times the rating for 4 seconds.

  When the instantaneous large power supply apparatus according to the present embodiment is adapted only to the instantaneous drop, only the voltage detector 10 that detects the voltage may be provided as in the conventional power supply stabilizing apparatus shown in FIG.

  Next, the SiC-CIJFET of the wide gap composite function semiconductor element used in the instantaneous high power supply device 1 of this embodiment will be described in detail. The reason why the converter 4 can be operated with electric power that greatly exceeds the rating in this embodiment is that the SiC-CIJFET, which is a wide gap composite functional semiconductor element, is used as the switching element.

  FIG. 3A is a top view of a SiC-CIJFET element (module) having a rated voltage and current of 8 kV · 400 A used in the present embodiment, and FIG. It is -b sectional drawing. This SiC-CIJFET element is modularized by connecting nine SiC-CIJFET chips 131-139 having a rated current of 45A in parallel. In FIG. 3B, nine intermediate lower electrodes 16 are provided on the source electrode 14, and nine CIJFET chips 131 to 139 having a substantially square shape with a side of 7 mm are provided on each intermediate lower electrode 16. Yes. An intermediate upper electrode 17 is provided on each CIJFET chip 131-139. A drain electrode 15 is provided in contact with all the intermediate upper electrodes 17, and nine CIJFET chips 131 to 139 are sandwiched between the source electrode 14 and the drain electrode 15. With this configuration, nine CIJFET chips 131 to 139 are connected in parallel between the source electrode 14 and the drain electrode 15. Spacers 18 are provided between the CIJFET chips 131 to 139 to define the positions of the CIJFET chips 131 to 139 on the cathode electrode 14. The ceramic envelope 19 is used to maintain and insulate between the source electrode 14 and the drain electrode 15 and has a diameter of about 10 cm.

  FIG. 4 shows a cross section of a SiC CIJFET cell, and FIG. 5 shows output characteristics. A plurality of CIJFET cells are arranged in parallel to constitute one CIJFET chip. In FIG. 4, the CIJFET cell is provided with an n-type drift layer 51 on the upper surface of a substrate 50 functioning as a drain of n-type SiC. A p-type buried gate layer 521 is formed in the upper region of the n-type drift layer 51, and p-type buried gate layers 522 and 523 are formed in both end regions. The p-type buried gate layer 521 faces the n-type source layer 54 with the n-type channel layer 53 interposed therebetween. A source electrode 56 is provided on the n-type source layer 54. P-type upper gate layers 524 and 525 are formed in contact with the p-type buried gate layers 522 and 523, respectively, and a gate electrode 57 serving as a control electrode is provided in the p-type upper gate layers 524 and 525. A drain electrode 55 is provided on the lower surface of the substrate 50. The p-type buried gate layers 521, 522 and 523 and the p-type upper gate layers 524 and 525 are electrically connected to the gate terminal 59.

  In the CIJFET cell of FIG. 4, when the drain electrode 55 is at a high potential and the source electrode 56 is at a low potential, the gate voltage applied to the gate electrode 57 as the control electrode is the same potential as that of the source electrode 56. The n-type channel layer 53 between the upper gate layers 524 and 525 and the p-type buried gate layer 521 is completely covered with a depletion layer around the gate pn junction, and the CIJFET cell is pinched off. Therefore, no current flows between the drain electrode 55 and the source electrode 56, and a high reverse withstand voltage is maintained. When a gate voltage higher than the voltage of the source electrode 56 is applied to the gate electrode 57 within a range smaller than the built-in voltage (about 2.7 V) of the gate pn junction, the CIJFET element 131 operates as a unipolar semiconductor element. That is, the pinch-off due to the depletion layer is eliminated, a channel is formed in the n-type channel layer 53, and a current due to electrons flows from the substrate 50 as the drain toward the n-type source layer 54. When the gate voltage is increased, the width of the depletion layer becomes narrower, and conversely, the channel width becomes wider and a larger current flows.

  FIG. 5 shows the voltage-current characteristics between the drain and source with the gate voltage VG as a parameter. As shown in FIG. 5, when the gate voltage VG is 2.5V and the drain-source voltage VDS is 4V, the drain-source current IDS becomes the rated current of 45A. When a gate voltage larger than the built-in voltage (about 2.7 V) of the gate pn junction is applied to the gate electrode 57, the CIJFET chip 131 operates as a bipolar semiconductor device. That is, holes are injected into the n-type channel layer 53 from the p-type buried gate layers 521, 522 and 523 and the p-type upper gate layers 524 and 525, and conductivity modulation occurs in the n-type channel layer 53. For this reason, the resistance of the n-type channel layer 53 is significantly reduced. Further, electrons are injected from the n-type source layer 54 and the n-type channel layer 53 into the p-type buried gate layer 521, and the electrons diffuse in the p-type buried gate layer 521 to reach the n-type drift layer 51. . In this case, the p-type buried gate layer 521 functions as a p-type base region, and the CIJFET operates in the same manner as the npn transistor. Therefore, a large current due to the current due to holes and the current due to electrons flows from the drain electrode 55 to the source electrode 56. For example, when the drain-source voltage VDS is 4 V and the gate voltage VG is 4 V, a drain-source current IDS of about 100 A, which is about 2.2 times the rated current, flows.

  The operation at the time of peak cut of the instantaneous large power supply device 1 including the converter 4 using the CIJFET having the above characteristics will be described below. At the time of peak cut, a gate voltage smaller than the built-in voltage (2.7 V) of the gate pn junction is applied to the gate electrode 57 of the CIJFET to operate the CIJFET as a unipolar semiconductor element. When the voltage drops, a gate voltage larger than the built-in voltage is applied to operate as a bipolar semiconductor device, and a current that is about 3.5 times larger than that when operating as a unipolar semiconductor device can flow for about 6 seconds. .

  Si-bipolar semiconductor elements using silicon (Si) as a base material have a negative temperature dependence in bipolar operation. Therefore, when a large current flows and the internal temperature of the element rises, the current further increases and the temperature rises further, and finally, thermal runaway occurs, leading to destruction of the element. When a plurality of Si-bipolar chips are connected in parallel, once current concentration occurs in a certain Si-bipolar chip, the current of other Si-bipolar chips may also be concentrated in that chip, leading to thermal runaway. . Therefore, it is difficult to use a large number of Si-bipolar chips connected in parallel.

  On the other hand, the internal resistance of the SiC-CIJFET has a positive temperature dependence. Therefore, when an excessive current flows and the element temperature rises, the internal resistance increases, the current is automatically reduced, the temperature rise is suppressed, and thermal runaway does not occur. If the time during which a large current flows is 10 seconds or less, a large number of SiC-CIJFET chips can be connected in parallel. The time during which a large current can flow is the time until the internal temperature of the chip rises and reaches the limit temperature at which the properties as a semiconductor can be maintained because the amount of heat generated inside each chip is greater than the amount of heat released. This time is determined depending on the structure of each chip, the current density, the structure of the module in which the chips are connected in parallel, and the like. In the configuration shown in FIG. 3, it was confirmed by experiments that no problem occurred for about 6 seconds when a current of about three times the rated current was passed. For example, a test that generates a sag for 8 seconds during a peak cut operation test of about 45 minutes was performed. We were able to supply possible power.

  The converter according to the present embodiment uses about 6 times the rated power for about 4.5 seconds necessary to prevent the influence of the instantaneous drop by utilizing the instantaneous high power operation capability of the SiC-CIJFET used as the switching element. Acts as a converter that converts power. Therefore, unlike the conventional converter using a silicon semiconductor element, it is not necessary to set the design value of the capacity of the converter to that of high power that takes into account the instantaneous drop. As the design value of the capacity, a capacity capable of supplying power at the time of peak cut, that is, a capacity capable of supplying a fraction of the power at the time of instantaneous drop is sufficient. As a result, it is possible to realize a significant reduction in size, weight, and cost of an instantaneous large power supply device that can cope with peak cut.

<< Second Embodiment >>
FIG. 6 is a block diagram of an instantaneous large power supply device 21 for load leveling using the power conversion device according to the second embodiment of the present invention. The instantaneous high power supply device 21 includes a secondary battery 22 using a sodium-sulfur battery with a rated voltage of 1.5 KV and a rated power of 1.5 MW, a bidirectional chopper circuit 23, a converter 24 and a transformer 25 as an example of a power converter. As in the case of the instantaneous high power supply device 1 of FIG. Other configurations are the same as those of the instantaneous large power supply device 1. In the present embodiment, the instantaneous large power supply device 21 functions as a stable power supply device for load leveling.

  “Load leveling” means that power is stored during times when demand is low, and is stored during times when demand is high, in order to cope with a phenomenon in which power demand varies greatly depending on the time of day. It means releasing electric power. The secondary battery 22 is charged with a constant power at night when power demand is low, for example, 8 hours from 22:00 to 6:00. In the daytime when electricity demand is particularly high, for example, 8 hours from 9:00 to 17:00, about 1.35 MW of power is supplied from the secondary battery 22. A switching element (not shown) of the chopper circuit 23 is a SiC-charge injection MOS field effect transistor (hereinafter referred to as CIMOSFET) having a voltage / current of 10 kV · 1400A. The switching element (not shown) of the converter 24 is a SiC-CIMOSFET having a voltage / current of 10 kV · 600 A. It is difficult to make a SiC-CIMOSFET having a large rated current with one chip, and the current that can flow through one SiC-CIMOSFET chip is about 40A. The SiC-CIMOSFET element (module) used for the converter 22 of this embodiment is provided with 15 pieces of CIMOSFET chips with a rated current of 40 A in a package similar to that shown in FIG. 3, and these are connected in parallel to form a module.

  As described above, since the rated current of SiC-CIMOSFET is relatively small, the voltage is increased to increase the rated power. For example, when 1.35 MW of electric power is supplied in the daytime, the chopper circuit 23 boosts the 1.5 kV DC output voltage of the secondary battery 2 to 3 kV. As a result, the converter 4 is supplied with DC power having a voltage / current of about 3 kV / 480 A. The converter 24 converts this DC power into AC power having a voltage / current of about 1.38 kV · 566 A and supplies the AC power to the transformer 25. The transformer 25 boosts the voltage of 1.38 kV to 6.6 kV and supplies it to the system bus 102 via the switch 6.

  When power supply 100 is supplied with power of 1.35 MW and a voltage drop due to a lightning strike occurs in power system 100, and the voltage of system bus line 102 significantly decreases due to the effect, a voltage decrease is detected by voltage detector 10, The detection output is input to the detection circuit 8. The detection circuit 8 generates a command signal for determining an operation mode based on the detection output and applies it to the mode switching circuit 13. The mode switching circuit 13 applies to the control circuit 9 a control signal that determines an operation mode for operating the SiC-CIMOSFET of the converter 4 as a unipolar semiconductor element or a bipolar semiconductor element. The control circuit 9 generates a PWM control signal based on the input control signal, inputs the PWM control signal to the converter 24, and drives the switching element of the converter 24. The output voltage of the secondary battery 22 is boosted to 4.5 kV by the chopper circuit 23 and supplied to the converter 24. The control circuit 9 applies a drive signal in which the pulse width of the PWM signal for switching control is expanded to the converter 24. Accordingly, the converter 24 outputs active power of about 1.35 MW, which is a rated value, and reactive power of about 6.44 MVAR at a voltage of about 2.07 kV. The output of the converter 24 is boosted by the transformer 25 and supplied to the system bus 102 to prevent a voltage drop of the system bus 102.

  In the instant large power supply apparatus of this embodiment, the converter can be operated with the electric power significantly exceeding the rating as described above because the SiC-CIMOSFET is used as the switching element.

  FIG. 7 shows a cross-sectional view of a SiC-CIMOSFET cell. In the SiC-CIMOSFET, an n-type drift layer 151 is formed on a substrate 150 that functions as a drain of n-type SiC. A p-type gate layer 652 is formed in the upper central region of the n-type drift layer 151. P-type gate layers 653 and 654 are formed in both end region of the drift layer 151, respectively. Other p-type gate layers 655 and 656 are formed on both p-type gate layers 653 and 654, respectively. An n-type channel layer 658 is formed in a region surrounded by the p-type gate layers 652, 653, and 654. An n-type source layer 659 is formed in the upper central region of the n-type channel layer 658. A drain electrode 160 is provided on the lower surface of the substrate 150, and a source electrode 161 is provided on the n-type source layer 659. P-type gate electrodes 661 and 662 are provided on the p-type gate layers 655 and 656, respectively. MOS gate electrodes 667 and 668 are provided on n-type channel layer 658 via MOS gate insulating layers 665 and 666, respectively. The p-type gate layers 652, 653, 654, 655, 656 are electrically connected to the p-type gate electrodes 661, 662 and are led out as a p-type gate terminal 670. The MOS gate electrodes 667 and 668 are electrically connected and led out as a MOS gate terminal 673.

  In the CIMOSFET cell, the gate voltage applied to the MOS gate electrodes 667 and 668 and the p-type gate electrodes 661 and 662 is applied to the source electrode 161 in a state where the voltage is applied with the drain electrode 160 at the high potential and the source electrode 161 at the low potential. The n-type channel layer 658 is completely covered with a depletion layer around the gate pn junction, and the SiC-CIMOSFET is pinched off. As a result, current does not flow between the drain electrode 160 and the source electrode 161, and the withstand voltage is high. A gate voltage higher than a predetermined threshold is applied to the MOS gate electrodes 667 and 668, and the p-type gate electrodes 661 and 662 are higher than the voltage of the source electrode 161 in a range smaller than the built-in voltage (about 2.7 V) of the gate pn junction. When a gate voltage is applied, the SiC-CIMOSFET operates as a unipolar semiconductor element. That is, the pinch-off due to the depletion layer is eliminated, a channel is formed in the n-type channel layer 658, and a current due to electrons from the drain electrode 160 toward the source electrode 161 flows. When the gate voltage applied to the p-type gate electrodes 661 and 662 is increased, the width of the depletion layer is narrowed. Therefore, the width of the channel is widened and a large current flows between the drain electrode 160 and the source electrode 161.

  When a voltage higher than the built-in voltage (2.7 V) of the gate pn junction is applied to the p-type gate electrodes 661 and 662, the CIMOSFET operates as a bipolar semiconductor element. That is, holes are injected into the n-type channel layer 658 from the p-type gate layers 652, 653, 654, 655, 656, conductivity modulation occurs in the n-type channel layer 658, and the resistance of the n-type channel layer 658 is remarkably increased. To reduce. Further, electrons are injected from the n-type source layer 659 and the n-type channel layer 658 to the p-type gate layer 652. These electrons diffuse in the p-type gate layer 652 and reach the n-type drift layer 151. In this way, the p-type gate layer 652 functions as a p-type base, and the CIMOSFET operates as an npn transistor. A current due to holes and a large current due to electrons flow from the drain electrode 160 to the source electrode 161.

  The chopper circuit 23 of the instantaneous high power supply device 21 and the switching element of the converter 24 shown in FIG. 6 of the present embodiment are connected in parallel to 15 chips each composed of a plurality of SiC-CIMOSFET cells, as shown in FIG. The one configured in a module similar to the one is used. In the module, the MOS gate electrodes 667 and 668 of 15 chips are connected in common, and the p-type gate electrodes 661 and 662 and the p-type gate layer 652 are connected in common. Further, the drain electrodes 160 of the 15 chips are connected in common, and the source electrodes 161 are connected in common.

  When the instantaneous high power supply device of this embodiment is used for a voltage drop, a bipolar voltage is applied by applying a gate voltage larger than the built-in voltage (about 2.7 kV) of the gate pn junction to the p-type gate electrodes 661 and 662 of the CIMOSFET. Operate as a semiconductor element. If the time for operating as a bipolar semiconductor element is about 5 seconds, a large current about 3.8 times larger than that when operating as a unipolar semiconductor element can be passed.

  In this example, by utilizing the instantaneous high power operation capability of SiC-CIMOSFET, a converter with a rated power of 1.5 MW is about 4.7 times as large as 1.5 MW in a short time to prevent the influence of a sag. It can be operated as a converter having a rated power equivalent to about 7 MW. Therefore, it is possible to realize an instantaneous large power supply device for load leveling that can cope with a sudden drop, which is significantly reduced in size, weight, and cost.

<< Third embodiment >>
A power converter according to a third embodiment of the present invention will be described with reference to FIG.

  FIG. 8 shows a block diagram of an example in which the instantaneous high power supply device of the present invention is applied to an induction heating device of 100 kW and 500 Hz class. In a heating device for rapidly heat-treating metal parts under high-precision temperature control, a low-temperature heating furnace is rapidly brought to a predetermined high temperature at the start of operation or during operation, and conversely a high-temperature heating furnace Is required to rapidly reach a predetermined low temperature. In particular, at the start of operation, larger electric power is required than when maintaining a predetermined high temperature in a steady operation state.

  In FIG. 8, a rectifier 301 is connected to a three-phase distribution system line 290 via a switch 292, and an input three-phase alternating current is rectified to obtain a direct current output at direct current output terminals 295 and 296. A large capacity capacitor 302 is connected between the DC output terminals 295 and 296, and the DC output charges the capacitor 302. An inverter 303 as an example of a power converter is connected between the DC output terminals 295 and 296. Output terminals 315 and 316 of the inverter 303 are connected to both terminals 319 and 320 of the heating coil 304 via respective capacitors 317 and 318. A temperature sensor 306 that detects the temperature in the heating furnace is provided in the vicinity of the heating coil 304, and the detection output is input to the detection circuit 309. Current detectors 307 and 308 such as CT are provided on two of the three-phase input lines of the rectifier 301, and the detection output is input to the detection circuit 309.

  A current detector 305 is also provided on the output line connected to the output terminal 315 of the inverter 303, and the detection output is input to the detection circuit 309. The output of the detection circuit 309 is applied to the mode switching circuit 300. The mode switching circuit 300 determines an operation mode for operating the switching elements 331 to 334 as a unipolar semiconductor element or a bipolar semiconductor element, and inputs a mode control signal to the control circuit 310. The four output terminals of the control circuit 310 are connected to the input terminals of the drive circuits 311, 312, 313 and 314 of the inverter 303. The output terminals of the drive circuits 311, 312, 313, and 314 are connected to the gates of the switching elements 331, 332, 333, and 334, respectively. A well-known flywheeling diode is connected between the source and drain of each of the switching elements 331 to 334.

  In the inverter 303, the switching elements 331, 332, 333, and 334 are composed of CIJFET modules having a rated voltage / current of 1 kV · 150 A. The configuration of the CIJFET module is similar to that of the first embodiment shown in FIG. The inverter 303 converts the direct current output of the rectifier 301 into an alternating current output, and supplies it to the induction heating coil 304 via the capacitors 317 and 318.

  The detection circuit 309 performs predetermined arithmetic processing based on the detection outputs of the current detectors 305, 307, and 308 and the detection output of the temperature detector 306, and applies the resulting command signal to the mode switching circuit 300. The mode switching circuit 300 applies a mode control signal for determining an operation mode to the control circuit 310 based on the command signal. The control circuit 310 generates four control signals according to the mode control signal and applies them to the drive circuits 311 to 314, respectively. Each drive circuit 311 to 314 generates a drive signal for each switching element 331 to 334 based on the input control signal, and applies it to each switching element.

  The induction heating apparatus needs to raise the temperature in the heating furnace to a predetermined temperature in a predetermined time (for example, 5 seconds to 30 seconds) according to the material, shape, and intended use of the metal part to be heat-treated. Therefore, normally, it is necessary to supply a large amount of power at the start of operation of the induction heating apparatus. In this embodiment, at the start of operation, the CIJFETs of the switching elements 331 to 334 are operated as bipolar semiconductor elements by the drive signals of the respective drive circuits 311 to 314, and the AC output power that is 3 to 5 times the steady state is heated by the heating coil 304. Can be supplied. It is desirable to operate the CIJFET as a unipolar semiconductor element in a steady state to prevent power loss in the CIJFET. If a capacitor having a large capacity is used, when the supply power to the heating coil 304 increases rapidly, the charge charged in the capacitor 302 compensates for the sudden increase in supply power. As a result, it is possible to prevent a decrease in the voltage of the distribution system line 290 due to a sudden increase in supply power.

  According to the present embodiment, the rated output of the inverter 303 of the induction heating device may be set in accordance with the output during steady operation, and when a large output is required in a short time such as at the start of operation or rapid heating, By operating the CIJFET of the switching elements 331 to 334 as a bipolar semiconductor element, it is possible to obtain an output that is 3 to 5 times the steady state. Accordingly, the induction heating device can be reduced in size, weight, and cost.

<< 4th Example >>
A power conversion apparatus according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 9 is a block diagram of an example in which the instantaneous large power supply device of the present invention is applied to a traveling motor 404 of an electric vehicle having a rated output of 60 kW. The rated frequency of alternating current applied to the traveling motor 404 is, for example, 18 kHz.

  In FIG. 9, a three-phase inverter 403 that is a power conversion device is connected to a battery 401 via a power switch 400. A capacitor 402 is connected between both terminals of the battery 401. The battery 401 is a secondary battery such as a lead battery, but may be a power generation device such as a fuel cell.

  A motor 404, which is a synchronous motor having a permanent magnet rotor, is connected to the three output terminals 415, 416, and 417 of the inverter 403. The rotation angle of the rotor of the motor 404 is detected by a shaft rotation angle detector 405 provided in the vicinity of the shaft connected to the rotor, and a detection signal indicating the rotation speed of the shaft is input to the detection circuit 408. The stator current of the motor 404 is detected by a current detector 420 such as CT, and a detection signal is input to the detection circuit 408. The detection circuit 408 further receives a torque request signal 407 output in response to the driver's operation of the accelerator pedal. The detection circuit 408 performs arithmetic processing based on the input both detection signals and the torque request signal, and inputs the resulting processing signal to the mode switching circuit 410. The mode switching circuit 410 applies a mode control signal for determining the operation mode of the switching elements 431 to 436 to the inverter control circuit 409. The control circuit 409 outputs control signals to the respective drive circuits 421, 422, 423, 424, 425, and 426 that drive the switching elements 431, 432, 433, 434, 435, and 436 of the inverter 403. The drive circuits 421 to 426 apply drive signals for driving the switching elements 431 to 436 to the gates that are control electrodes of the respective switching elements 431 to 436 based on the input control signals. A flywheeling diode is connected between the source and drain of each of the switching elements 431 to 436.

  As the switching elements 431 to 436 of the inverter 403 in the instantaneous large power supply apparatus of the present embodiment, the CIMOSFET module shown in FIG. 7 and described in the second embodiment is used.

  In the case of an electric vehicle, it is necessary to supply the motor 404 with electric power several times that in normal driving, although it is a short time when the vehicle starts suddenly or escapes when a tire enters a muddy state. The switching elements 431 to 436 of the inverter 403 in this embodiment are, for example, CIMOSFET modules with rated voltage and current of 1 kV · 600 A class. When it is necessary to supply a large amount of power to the motor 404, such as when starting or accelerating the electric vehicle, the processing signal of the detection circuit 408 corresponding thereto is input to the mode switching circuit 410, and the mode control signal corresponding thereto is input to the inverter control circuit. 409 is applied. The inverter control circuit 409 applies a positive voltage to the MOS gate terminal 673 and the p-type gate terminal 670 of the switching elements 431 to 436, which are the control electrodes of the CIMOSFET element shown in FIG. 7, according to the applied control signal. For example, the MOS gate voltage is 5 to 30V and the p-type gate voltage is 2.7 to 25V. Accordingly, the CIMOSFET element operates as a bipolar semiconductor element, and the inverter 403 can supply AC power about 1.5 to 4 times the rated power to the motor 404. The time for which the inverter 403 can output AC power 1.5 to 4 times the rated power is, for example, about 2 to 20 seconds. The secondary battery 401 and the automobile fuel cell can supply electric power several times the rated power for a short time.

  During normal driving of the electric vehicle, a voltage of 1.0 to 2.5 V is applied to the p-type gate terminal 670 of the CIMOSFET element, and a voltage of 5 to 30 V is applied to the MOS gate terminal 673. Thereby, the CIMOSFET element operates as a unipolar semiconductor element.

  In the conventional inverter having a switching element using silicon, it is necessary to configure the inverter by using a switching element having a rated power of 1.5 to 4 times the rated output. In this embodiment, the inverter is unipolar. By using a wide gap composite function semiconductor element capable of selecting operation and bipolar operation, it is possible to cope with large power several times the rated power by using an inverter having a rated power substantially equal to the output power during normal driving. As a result, the inverter for an electric vehicle motor can be significantly reduced in size, weight, and cost.

  The present invention has been described with reference to the first to fourth embodiments. However, the present invention is not limited to these embodiments, and various modifications can be applied.

  For example, the wide gap composite function semiconductor element of the switching element is not limited to CIJFET or CIMOSFET. In addition, a wide gap semiconductor material other than SiC, that is, a semiconductor element made of gallium nitride, diamond, or the like can be used for the converter and the inverter in the same manner. A composite functional element made of Si can also be used. The wide gap composite function semiconductor element can also be used as a switching element of a switching power supply.

  The battery may be a zinc chloride battery, a zinc bromine battery, a lithium ion battery, etc., in addition to a redox flow battery, a sodium sulfur battery, a lead battery, a fuel battery, and the like.

  In the case of an instantaneous large power supply device with a small capacity of 200 kW or less, the current capacity is small, so that a wide-gap bipolar semiconductor element with a small chip area can be adequately accommodated. In this case, a chopper circuit for boosting the voltage to obtain predetermined power with a small current is not necessarily required, and the output of the battery may be directly applied to a power conversion device such as an inverter.

  Wide-gap bipolar semiconductor devices can be easily realized with high breakdown voltage. For example, in the first and second embodiments, a high breakdown voltage of 20 kV or higher can be directly connected to the 6.6 kV system bus 102. Therefore, it is possible to use only the interconnecting reactor without using a transformer.

  In the first and second embodiments, the example of the 6.6 kV distribution system bus has been described. However, by making each element constituting the instantaneous large power supply device have a high withstand voltage and large current, the power system can be further upstream. It can also be applied to an instantaneous large power supply device to be connected. In addition, the instantaneous high power of the present invention can be applied to a relatively long “instantaneous power outage” exceeding a few minutes when a small animal such as a snake or a bird is caught on a power transmission line or a short circuit or ground fault occurs due to contact with a tree. Supply device can be applied. In addition, if one of the generators of the power transmission power supply fails or the load (factory, etc.) of a large power customer suddenly stops operating, sudden power fluctuations occur, resulting in an imbalance between power supply and demand. May last more than a minute. Increasing the capacity of the secondary battery and cooling the switching element against fluctuations in the grid frequency due to an imbalance in power supply and demand for 5 minutes to 1 hour, which is much longer than the duration (several seconds) of the instantaneous drop due to lightning The instantaneous high power supply device of the present invention can be applied by taking means for keeping the temperature below a predetermined value. In the case of such a long time, the instantaneous large power supply apparatus of the present invention can adjust power about 1.5 to 3 times the rated output, and can be used as an emergency wire.

  The power conversion device of the present invention functions as a unipolar semiconductor element when the gate voltage is lower than the built-in voltage of the gate junction, and functions as a bipolar semiconductor element when the gate voltage is high. A wide gap composite function semiconductor element having a combination is used as a switching element. During normal operation when the power system is operating at power lower than the rated power, the wide gap composite function semiconductor element is operated as a unipolar semiconductor element. It is operated as a bipolar semiconductor element at the start of operation (hereinafter referred to as “device start-up”) when various devices (loads) are started, which require instantaneous power loss or instantaneous high power. As a result, the power conversion device normally operates at the rated power, and operates at a power that greatly exceeds the rated power when an instantaneous high power is supplied such as when the voltage drops or when the device is started. Since the large power supply time is short, the semiconductor element is not destroyed.

  The instantaneous large power supply device using the power conversion device of the present invention is connected between a secondary battery that charges and discharges DC power, and the secondary battery and a system bus of a power transmission power source. As a power converter that converts input AC to DC and outputs it to the secondary battery, converts DC output from the secondary battery to AC and outputs it to the system bus, a switching element is a wide gap composite It has the converter which is a power converter device comprised by the functional semiconductor element.

  A wide gap composite function semiconductor device operates unipolar when operating below the rated power. During bipolar operation, power that is 1.5 to 20 times the rated power during unipolar operation can be controlled for a short time. When a high-performance heat sink is used, power of 1.4 to 5 times the rated power can be controlled within a few minutes. In the present invention, the rated power at the time of unipolar operation of the wide gap composite function semiconductor element used for the switching element of the converter is set to a value of “normal time” when the load is operating in a steady state. In the event of a momentary drop when a large amount of power needs to be supplied in a short time (when the power supply voltage drops significantly for a few seconds or less due to lightning, etc.) or during an instantaneous power outage (a relatively long power outage exceeding several minutes) When generated, the converter, which is a power conversion device, is operated with power during bipolar operation that greatly exceeds the rated power during normal operation. In the bipolar operation, the gate drive current is larger than in the unipolar operation, and the loss due to the gate current is greatly increased. However, since the bipolar operation is a short time, the increase in power loss due to this is a level that can be ignored in practice.

Another instantaneous large power supply device using the power conversion device of the present invention is a secondary battery that charges and discharges a direct current,
A bidirectional chopper circuit that is connected to the secondary battery, steps down the charging voltage of the secondary battery, and boosts the discharge voltage of the secondary battery, and is connected between the chopper circuit and the system bus of the power transmission power source. A switching element that converts alternating current input from the system bus into direct current and outputs it to a chopper circuit, converts direct current input from the chopper circuit into alternating current and outputs the alternating current to the system bus is a wide gap composite function semiconductor element The converter which is the power converter device comprised by is provided.

  In the instantaneous large power supply device using the power conversion device of the present invention, the charging voltage of the secondary battery is stepped down by the bidirectional chopper circuit, and the discharge voltage is boosted. The instantaneous high power supply device can be applied to a system bus having a voltage higher than the voltage.

Another instantaneous large power supply device using the power conversion device of the present invention is a secondary battery that charges and discharges DC power,
A bidirectional chopper circuit connected to the secondary battery, stepping down a charging voltage of the secondary battery and boosting a discharge voltage of the secondary battery;
Connected between the chopper circuit and the system bus of the power transmission power source, converts alternating current input from the system bus to direct current and outputs it to the chopper circuit, and converts direct current input from the chopper circuit to alternating current A converter that is a power conversion device in which the switching element that outputs to the system bus is configured with a wide gap composite function semiconductor element,
A detection device that detects a voltage of the system bus and detects a supply and demand state of power based on the detected voltage, and a load connected to the system bus and a power transmission power source based on a detection output of the detection device A control circuit that controls the converter to charge the secondary battery when the supply and demand of power is balanced, and to discharge the secondary battery and supply power to the system bus when the demand exceeds the supply Have.

  According to the present invention, in addition to the above effect, the occurrence of a sag is detected by detecting the voltage of the system bus, and the power of the system at the time of the sag is supplied by supplying power from the secondary battery to the system bus. Voltage drop can be prevented.

Another instantaneous large power supply device using the power conversion device of the present invention is a secondary battery that charges and discharges DC power,
A bidirectional chopper circuit connected to the secondary battery, stepping down a charging voltage of the secondary battery and boosting a discharge voltage of the secondary battery;
Connected between the chopper circuit and the system bus of the power transmission power source, converts alternating current input from the system bus to direct current and outputs it to the chopper circuit, and converts direct current input from the chopper circuit to alternating current A converter that is a power conversion device in which the switching element that outputs to the system bus is configured with a wide gap composite function semiconductor element,
A detection device that detects the voltage and current of the system bus, and detects a supply and demand state of the power of the load based on the detected voltage and current, and is connected to the system bus based on a detection output of the detection device When the supply and demand of power between the load and the power transmission power supply is balanced, the secondary battery is charged, and when the demand exceeds the supply, the secondary battery is discharged to supply power to the system bus. A control circuit for controlling the converter;

  According to the present invention, in addition to the above effects, the supply and demand situation of the power of the system can be detected by detecting the voltage and current of the system bus. Since the power supply / demand situation can be detected, the instantaneous large power supply device using the power conversion device of the present invention can be used for load leveling.

  Another instantaneous high-power supply device using the power conversion device of the present invention is the secondary battery from the secondary battery when the voltage of the system bus is drastically reduced for a short time due to a lightning accident or the like. 2 to 12 times the rated discharge power of the converter, and the converter converts the discharge power of the secondary battery corresponding to 2 to 12 times the rated control power of the converter into an alternating current to a predetermined value. It is controlled by the control circuit so as to output reactive power and active power 2 to 12 times the rated power to the system bus.

  When the voltage of the system bus is instantaneously reduced, the secondary battery outputs a discharge power that is twice to 12 times the rated discharge power of the secondary battery, and the converter starts from twice the rated control power of the converter. It is controlled by the control circuit so that the discharge power of the secondary battery corresponding to 12 times is converted into an alternating current, and a predetermined reactive power and an active power smaller than twice the rated power are output to the system bus. Features.

  A connection reactor is provided between the system bus and the converter.

  The secondary battery is a redox flow battery or a sodium sulfur battery.

  The wide gap composite functional semiconductor element is a charge injection junction field effect transistor (CIJFET) using silicon carbide (SiC) as a base material.

  The wide gap composite functional semiconductor device is a semiconductor device using gallium nitride as a base material.

  The composite function wide gap bipolar semiconductor element is formed by connecting at least one chip or a plurality of chips of SiC CIJFET in parallel.

  The wide gap bipolar semiconductor element is formed of at least one chip or a plurality of chips of SiC CIMOSFETs connected in parallel.

Another instantaneous large power supply device using the power conversion device of the present invention is a secondary battery that charges and discharges DC power,
A bidirectional chopper circuit connected to the secondary battery, stepping down a charge voltage of the secondary battery, and stepping up a discharge voltage of the secondary battery;
Connected between the chopper circuit and the system bus of the power transmission power source, converts alternating current input from the system bus to direct current and outputs it to the chopper circuit, and converts direct current input from the chopper circuit to alternating current A converter that is a power conversion device in which the switching element that outputs to the system bus is configured with a wide gap composite function semiconductor element,
A detection device that detects the frequency of the system bus, detects a power supply / demand state based on the detected frequency, and a load connected to the system bus based on a detection output of the detection device, and a power transmission power source Control to control the converter so that the secondary battery is charged when the supply and demand of power is balanced, and when the demand exceeds the supply, the secondary battery is discharged to supply power to the system bus It has a circuit.

  Another instantaneous large power supply device using the power conversion device of the present invention includes a secondary battery that charges and discharges DC power, and the secondary battery and a load connected to a system bus of the power transmission power source. A wide gap bipolar semiconductor element connected as a switching element, converting alternating current input from the system bus to direct current and outputting to the secondary battery; converting direct current output from the secondary battery to alternating current And a converter that is a power conversion device that outputs to the load.

  The instantaneous large power supply device further detects the voltage and current of the power supplied to the load connected to the system bus, and detects the supply and demand state of the power of the load based on the detected voltage and current. Based on the detection device and the detection output of the detection device, when the power supply and demand of the load and the power transmission power supply is balanced, the secondary battery is charged, and when the demand exceeds the supply, A control circuit that controls the converter to discharge the secondary battery and supply power to the system bus;

  Another instantaneous high-power supply device using the power conversion device of the present invention is a unipolar semiconductor that is connected between a DC power source that supplies DC power and the DC power source and a load, and is controlled by a control electrode as a switching element. Wide-gap composite that has a composite function to select whether to operate as an element or a bipolar semiconductor element, normally operates as a unipolar semiconductor element, and operates as a bipolar semiconductor element when instantaneous high power is required A power conversion device that includes a functional semiconductor element, converts DC power input from the DC power source into AC power, and outputs the AC power to the load.

  The direct current power source includes a rectifier that converts alternating current of a power system into direct current, and a capacitor connected between the positive and negative output terminals of the direct current of the rectifier.

  The DC power source is a secondary battery or a fuel cell.

  The wide gap composite functional semiconductor element is either a charge injection junction field effect transistor (CIJFET) or a charge injection MOS field effect transistor (CIMOSFET) using silicon carbide (SiC) as a base material. And

FIG. 1 is a block diagram of an instantaneous high power supply device for peak cut using the power conversion device of the first embodiment of the present invention. FIG. 2 is a block diagram of another example of the instantaneous high power supply apparatus for peak cut according to the first embodiment of the present invention. 3A is a plan view of a SiC-CIJFET module used in the converter of the first embodiment, and FIG. 3B is a cross-sectional view taken along line bb in FIG. FIG. 4 is a cross-sectional view of a SiC-CIJFET cell. FIG. 5 is a graph showing the drain-source voltage-current characteristics of the SiC-CIJFET with the gate voltage as a parameter. FIG. 6 is a block diagram of an instantaneous large power supply apparatus for load leveling using the power conversion apparatus according to the second embodiment of the present invention. FIG. 7 is a cross-sectional view of a SiC-CIMOSFET cell. FIG. 8 is a block diagram of an instantaneous high power supply apparatus for induction heating using the power conversion apparatus of the third embodiment of the present invention. FIG. 9 is a block diagram of an instantaneous high power supply device for a travel motor of an electric vehicle using the power conversion device of the fourth embodiment of the present invention. FIG. 10 is a block diagram of a stable power supply apparatus for peak cut using a conventional power conversion apparatus.

1, 21 Instantaneous large power supply device 100 Power system 4, 24 Converter 5, 120 Transformer 6, 109, 111, 114, 115 Switch 10 Voltage detector 11 Current detector 131-139 SiC-CIJFET chip 50, 150 Substrate 55, 160 Drain electrode 56, 161 Source electrode 57 Gate electrode 667, 668 MOS gate electrode 661, 662 P-type gate electrodes 311-314, 421-426 Drive circuit 331-334, 431-436 Switching element 303, 403 Inverter

Claims (6)

A wide gap composite function semiconductor element having a composite function for selecting whether to operate as a unipolar semiconductor element or a bipolar semiconductor element by control by a control electrode,
Using the wide gap composite function semiconductor element as a switching element, performing at least one of an operation of converting AC to DC and outputting, or an operation of converting DC to AC and outputting, or DC to DC While performing the conversion and output operation,
The wide-gap multi-functional semiconductor device is in the normal operating as said unipolar semiconductor device, the bipolar semiconductor device operating you wherein power converter that as when in need of instantaneous large power. The power converter according to claim 1, wherein the wide gap composite function semiconductor element is a charge injection junction field effect transistor (CIJFET) having silicon carbide (SiC) as a base material. The wide gap composite functional semiconductor element is formed by connecting in parallel at least one chip or a plurality of chips of a charge injection junction field effect transistor (CIJFET) using the silicon carbide (SiC) as a base material. The power converter according to claim 2 characterized by things. 2. The power conversion device according to claim 1, wherein the wide gap composite functional semiconductor element is a charge injection MOS field effect transistor (CIMOSFET) using silicon carbide (SiC) as a base material. The wide gap composite functional semiconductor element is formed by connecting in parallel at least one chip or a plurality of chips of a charge injection MOS field effect transistor (CIMOSFET) using the silicon carbide (SiC) as a base material. The power conversion device according to claim 4 . The power converter according to claim 1, wherein the wide gap composite functional semiconductor element is a semiconductor element having gallium nitride as a base material.

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