JP2004236469A - Instantaneous high power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small, lightweight and low cost instantaneous high power supply having a power converter capable of supplying a power exceeding the normal power significantly at the time of starting or momentarily stoppage or upon occurrence of momentary power interruption while employing a power converter having a rated power corresponding to a normally required power. <P>SOLUTION: The instantaneous high power supply comprises a secondary battery, a bidirectional chopper circuit and a bidirectional converter wherein the switching element of the converter comprises a wide gap multifunction semiconductor element. The instantaneous high power supply utilizes the instantaneous high power operation capability at the time of bipolar operation and the instantaneous high power operation capability of the secondary battery. During a short time when the effect of momentary power interruption is blocked, the switching element is operated as a bipolar semiconductor element and the converter is operated with a power capacity exceeding the instantaneous high power operation capability of the secondary battery and several times as high as the rated capacity. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an instantaneous large power supply device capable of supplying a large amount of power exceeding a rating for a short time.
[0002]
[Prior art]
In recent years, electronic devices that are sensitive to fluctuations in the power supply voltage, such as personal computers and precision electronic devices equipped with a precision motor, have been frequently used. For this reason, there is an increasing demand for measures against instantaneous voltage drop (hereinafter, abbreviated as “sag”), which is a phenomenon in which the power supply voltage drastically drops for a few seconds or less. As a device for measures against instantaneous voltage drop, there is a stable power supply device capable of supplying large power for a short time only when the voltage drops, and the demand for the device is increasing. In addition, conventional power leveling devices, peak cut devices, frequency fluctuation suppression devices, voltage stabilization devices, flicker suppression devices, etc. It is required to add a capability to supply large power although it is time (hereinafter, referred to as “instant large power supply capability”). Furthermore, an electric heating device, a lighting device using a large number of large light bulbs, and the like also require an instantaneous large power supply capability. That is, since the temperature of the coil heater is low when the operation of the electric heating device or the lighting device is started, the resistance is lower than that in the normal operation. Therefore, a large current flows, and the power converter is required to have an instantaneous large power supply capability.
[0003]
In addition, in induction heating equipment for metal heat treatment, in order to quickly heat-treat metal parts etc. under high-precision temperature control, the temperature of the heating furnace in the low-temperature state at the start of operation is quickly raised to a predetermined high temperature or rapidly raised to a predetermined temperature. It is necessary to set the temperature to be low. Therefore, a large amount of electric power is required at the start of the operation as compared with the case where the high temperature is maintained in the steady operation state. Such power in a short time but when large power needs to be supplied is referred to as “instant large power”, and a device for supplying instantaneous large power is referred to as “instant large power supply device”. At the start of operation, a motor or the like also needs large power to start rotating from a stationary state, and a power conversion device for a motor is required to have an instantaneous large power supply capability. In an electric vehicle or the like, it is necessary to drive the motor with electric power for a short time but larger than that during normal running when the vehicle escapes when starting or when a tire enters mud. There are various types of load devices that require instantaneous high power. Hereinafter, a conventional technology will be described by taking a power stable supply device which is a conventional instantaneous large power supply device as an example. The time when the load such as the load leveling device, the peak cut device, etc., the stable power supply device, the electric heating device, the lighting device, the motor device, etc. is operating in a steady state is hereinafter referred to as “normal time”.
[0004]
FIG. 10 is a block diagram of a power supply system including a conventional stable power supply device 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 device 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 of large customers who need particularly stable power supply, such as a semiconductor manufacturing factory and a precision machining factory. A general load 110 is also connected to the system bus 102 via switches 109 and 111. The power stable supply device 101 mainly includes a transformer 106 also serving as an interconnection reactor, a converter 107 for converting AC power to DC power or vice versa, and a large-capacity secondary battery 108 (redox flow battery). Have. This stable power supply device 101 normally functions as a peak cut device or a load leveling device, but in the event of a momentary voltage drop due to a lightning accident or the like, an instantaneous voltage drop to prevent the operation of the important loads 104 and 105 from being stopped. It also works as a preventive device.
[0005]
Hereinafter, the function of the stable power supply device 101 will be described in detail. In a “steady state” in which the supply and demand of power of the power supply system connecting the substation 130 and the important loads 104 and 105 and the general load 110 is in a “normal state”, the switch 103 and the transformer 103 are connected from the system bus 102. AC power is supplied to the stable power supply device 101 via 106. AC power is converted into DC power by converter 107 and stored in secondary battery 108. When the power consumption of the important load 104 or 105 is significantly increased and the power supplied to the load 104 or 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 DC power from the discharge of the secondary battery 108 into AC power by the converter 107, and supplies the excess active power to the system bus 102 to stabilize supply and demand. Let it. This function is called “peak cut” because the power stabilizing supply device 101 can supply the excess power to be supplied from the substation 130 to the system bus 102 instead, and cut the peak of the power supplied to the system bus 102. In.
[0006]
When the capacity of the secondary battery 108 of the stable power supply device 101 is increased so that power that can be supplied for a long time can be stored, it can be used as a load leveling device. That is, the secondary battery 108 is stored with constant power for a fixed time (typically about 8 hours) in a low demand time zone at night, and for a certain time (typically about 8 hours) in a high demand time zone in the daytime. Power is supplied from the secondary battery 108 at a constant power. Thus, in the high demand time zone, it is possible to supply more power than can be supplied by the substation 130. A stable power supply for this purpose is called a “load leveling device” because it leveles a large gap between day and night power demand.
[0007]
When lightning arrives at the power system 100 and a voltage sag occurs in the system voltage, the voltage detector 10 detects the voltage sag. In order to prevent the important loads 104 and 105 from stopping operation due to a voltage sag, it is necessary to immediately return to the system voltage before the voltage sag. For this purpose, the power stable supply device 101 controls the converter 107 by the control circuit 9 to supply 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 supply of power. When the power supplied from the secondary battery 108 is insufficient, the switch 109 is opened to disconnect the low-importance general load 110, and desired power is supplied to at least only the important loads 104 and 105 to supply the important loads 104 and 105. To prevent the suspension of operation. As soon as the sag has recovered, converter 107 returns to its normal operating state and supplies power from substation 130.
[0008]
In the conventional stable power supply device, at the time of peak cutting or load leveling, for example, the power of about 500 kW for the former and about 2 MW for the latter for a relatively long time (for example, about 1 hour for the former and about 8 hours for the latter) Need to supply. When lightning strikes during a peak cut or load leveling operation and a momentary voltage drop occurs, power of 1 MW to several MW is added for a relatively short time (for example, 2 seconds) to recover the lowered voltage, although it is a relatively short time (for example, 2 seconds). Need to supply.
[0009]
[Patent Document 1]
JP 2002-84683 A
[Patent Document 2]
JP-A-11-32438
[Patent Document 3]
International Publication Number WO98 / 43301
[Patent Document 4]
International Publication Number WO00 / 22679
[Patent Document 5]
JP-A-2000-252475
[0010]
[Problems to be solved by the invention]
A distribution line to which a load requiring instantaneous high power is connected when starting an electric heating device, a lighting device using a light bulb, a motor, or the like usually has an instantaneous high power supply capability. A heater, a light bulb for a vehicle, a secondary battery for supplying power to a motor, a fuel cell for an electric vehicle, and the like also have an instantaneous large power supply capability. Secondary batteries used for stable power supply, such as redox flow batteries, sodium-sulfur batteries, and lead batteries, can supply a much larger current than their rating in a short time of several seconds to several minutes. have. That is, a current several times as large as a rated current that can be supplied at normal times can be supplied for several seconds to several minutes. 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, a silicon (Si) semiconductor element used as a switching element of the converter 107, which is a power conversion device of the conventional stable power supply device, does not have an ability to control 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.
[0011]
When starting the operation of the lighting device using the electric heating device and the electric bulb, the time required for the temperature of the coil heater to rise to a steady state, or the time required for the motor to start and reach a predetermined rotating state, is a full operation. This is a very short time compared to the time. In addition, in the stable power supply device, a voltage sag due to the arrival of lightning does not occur so frequently, and is at most about 20 times a year. The duration of the sag due to the lightning is several seconds even in the case of multiple lightning. In rare cases, small animals such as snakes and birds may get caught on the transmission line, or trees may come into contact with each other, resulting in short circuits and ground faults. In such a case, an "instantaneous power outage" of a relatively long time exceeding several minutes may occur. However, in order to cope with such a short-time voltage sag or instantaneous power outage in the event of an instantaneous power outage, it is not possible to provide a power converter such as a large converter having a power rating several times that of normal power. There is a problem that not only the large power supply device becomes large and the equipment cost is high, but also the maintenance cost is high.
[0012]
The present invention uses a semiconductor element whose operation mode can be selectively changed between a normal time and a time when instantaneous high power is required by control by a control electrode. With this, while using a power converter having a power rating corresponding to the power required at normal times, there is a power converter capable of supplying power significantly exceeding normal power at the time of device startup, instantaneous voltage drop, instantaneous power failure occurrence It is an object of the present invention to provide a small, lightweight, and low-cost instantaneous large power supply device.
[0013]
[Means for Solving the Problems]
The power converter provided in the instantaneous large power supply 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 higher. A semiconductor element having both functions of a bipolar semiconductor element and a function (hereinafter, referred to as a “multifunctional semiconductor element”) is used as a switching element. During normal times when the power system operates at a power lower than the rated power, the multifunctional semiconductor device is operated as a unipolar semiconductor device. At the start of operation when various devices (loads) that require instantaneous voltage drop or instantaneous high power are required (hereinafter, referred to as “device startup”), they are operated as bipolar semiconductor elements. As a result, the power converter operates at the rated power in the normal state, and operates at the power greatly exceeding the rated power at the moment of instantaneous large power supply such as at the time of an instantaneous drop or at the start of the apparatus. Since the large power supply time is short, the semiconductor element is not destroyed.
The instantaneous large power supply device of the present invention is a secondary battery that charges and discharges DC power, and is connected between the secondary battery and a system bus of a power transmission power supply, and converts AC input from the system bus into DC. As a power conversion device that converts the direct current output from the secondary battery into an alternating current and outputs the alternating current to the system bus, as a power conversion device configured with a multifunction semiconductor element as a switching element. It has a converter that is a conversion device.
[0014]
The multifunction semiconductor element performs a unipolar operation when operating at or below the rated power. At the time of the bipolar operation, power of 1.5 to 20 times the rated power at the time of the unipolar operation can be controlled for a short time. In the case of using a high-performance heat sink, power of 1.4 to 5 times the rated power can be controlled for several minutes. In the present invention, the rated power during the unipolar operation of the multifunctional semiconductor element used as the switching element of the converter is set to the value of “normal time” in which the load operates in a steady state. In the event of an instantaneous voltage drop when a large amount of power needs to be supplied in a short period of time (when the power supply voltage drops for a short period of time of several seconds or less due to lightning, etc.) or an instantaneous power failure (for a relatively long (When it occurs), the converter, which is a power conversion device, is operated with the 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 increases significantly. However, since the bipolar operation is performed in a short time, the increase in power loss due to this operation is practically negligible.
[0015]
An instantaneous large power supply device according to another aspect of the present invention is a secondary battery that charges and discharges a DC current, is connected to the secondary battery, reduces a charge voltage of the secondary battery, and increases a discharge voltage of the secondary battery. Bidirectional chopper circuit, and
It is connected between the chopper circuit and the system bus of the power transmission power supply, converts AC input from the system bus into DC and outputs it to the chopper circuit, and converts DC input from the chopper circuit into AC. And a switching element that outputs the signal to the system bus.
In the instantaneous large power supply device of the present invention, the charging voltage of the secondary battery is reduced by the bidirectional chopper circuit, and the discharge voltage is increased, so that in addition to the above-described effects, the secondary battery has a voltage higher than the voltage of the secondary battery. The instantaneous large power supply device can also be applied to the system bus.
[0016]
An instantaneous large power supply device according to another aspect of the present invention is a secondary battery that charges and discharges DC power, is connected to the secondary battery, reduces the charge voltage of the secondary battery, and increases the discharge voltage of the secondary battery. Bidirectional chopper circuit,
It is connected between the chopper circuit and the system bus of the power transmission power supply, converts AC input from the system bus into DC and outputs it to the chopper circuit, and converts DC input from the chopper circuit into AC. A converter which is a power converter in which a switching element that outputs to the system bus is configured by a multifunctional semiconductor element;
A detection device that detects a voltage of the system bus, and a detection device that detects a power supply and demand state based on the detected voltage; and, based on a detection output of the detection device, a load and a power transmission power supply connected to the system bus. When the supply and demand of power are balanced, the control circuit controls the converter to charge the secondary battery and to discharge the secondary battery and supply the power to the system bus when the demand exceeds the supply. Have.
According to the present invention, in addition to the above effects, the occurrence of a sag is detected by detecting the voltage of the system bus, and power is supplied from the rechargeable battery to the system bus so that the Voltage drop can be prevented.
[0017]
An instantaneous large power supply device according to another aspect of the present invention is a secondary battery that charges and discharges DC power, is connected to the secondary battery, reduces the charge voltage of the secondary battery, and increases the discharge voltage of the secondary battery. Bidirectional chopper circuit,
It is connected between the chopper circuit and the system bus of the power transmission power supply, converts AC input from the system bus into DC and outputs it to the chopper circuit, and converts DC input from the chopper circuit into AC. A converter which is a power converter in which a switching element that outputs to the system bus is configured by a multifunctional semiconductor element;
A detection device that detects a voltage and a current of the system bus, and detects a supply and demand state of the power of the load based on the detected voltage and the current; and
Based on the detection output of the detection device, when the supply and demand of power of the load and the power transmission power supply connected to the system bus are balanced, when charging the secondary battery, when the demand exceeds the supply, A control circuit that controls the converter to discharge the secondary battery and supply power to a system bus.
According to the present invention, in addition to the effects described above, by detecting the voltage and current of the system bus, it is possible to detect the supply and demand situation of the system power. Since the power supply and demand situation can be detected, the instantaneous large power supply device of the present invention can be used for load leveling.
[0018]
The instantaneous high-power supply device according to another aspect of the present invention is characterized in that the voltage of the system bus is drastically reduced for a short period of time due to the occurrence of a lightning accident or the like, from the secondary battery, the rated discharge power of the secondary battery. The converter outputs a discharge power of 2 to 12 times the power of the secondary battery, and the converter converts the discharge power of the secondary battery equivalent to 2 to 12 times the rated control power of the converter into an alternating current to obtain a predetermined reactive power and a predetermined reactive power. It is controlled by the control circuit so as to output 2 to 12 times the active power to the system bus.
When the voltage of the system bus is dropped, the secondary battery outputs discharge power twice to 12 times the rated discharge power of the secondary battery. The control circuit is configured to convert discharge power of the secondary battery corresponding to 12 times into AC and output predetermined reactive power and active power smaller than twice the rated power to a system bus. Features.
An interconnection reactor is provided between the system bus and the converter.
The secondary battery is a redox flow battery or a sodium-sulfur battery.
[0019]
The multifunctional semiconductor device is a charge injection junction field effect transistor (CIJFET) using silicon carbide (SiC) as a base material.
The multifunctional semiconductor device is a semiconductor device containing gallium nitride as a base material.
The multi-function wide-gap bipolar semiconductor device is characterized in that at least one chip or a plurality of chips of a SiC CIJFET are connected in parallel.
[0020]
The wide-gap bipolar semiconductor element is formed by connecting at least one chip or a plurality of chips of a SiC CIMOSFET in parallel.
An instantaneous large power supply device according to another aspect of the present invention is a secondary battery that charges and discharges DC power, is connected to the secondary battery, reduces the charging voltage of the secondary battery, and discharges the secondary battery. Bidirectional chopper circuit to boost the
It is connected between the chopper circuit and the system bus of the power transmission power supply, converts AC input from the system bus into DC and outputs it to the chopper circuit, and converts DC input from the chopper circuit into AC. A converter which is a power converter in which a switching element that outputs to the system bus is configured by a multifunctional semiconductor element;
A detecting device that detects a frequency of the system bus, and detects a power supply / demand state based on the detected frequency; and
Based on the detection output of the detection device, when the load connected to the system bus and the supply and demand of power with the power transmission power supply are balanced, charge the secondary battery, and when the demand exceeds the supply A control circuit for controlling the converter to discharge the secondary battery and supply power to a system bus.
[0021]
An instantaneous high power supply device according to another aspect of the present invention is a secondary battery that charges and discharges DC power, and is connected between the secondary battery and a load connected to a system bus of a power transmission power supply, and has a switching function. A wide-gap bipolar semiconductor device is provided as an element, and the AC input from the system bus is converted to DC and output to the secondary battery, and the DC output from the secondary battery is converted to AC to the load. It has a converter which is a power converter for outputting.
The instantaneous large power supply device further detects a voltage and a current of the power supplied to the load connected to the system bus, and detects a supply and demand state of the power of the load based on the detected voltage and the current. Based on the detection output of the detection device and the detection device, the load, when the power supply and demand of the power transmission power supply is balanced, when charging the secondary battery, when the demand exceeds the supply, A control circuit for controlling the converter to discharge the secondary battery and supply power to the system bus.
[0022]
An instantaneous large power supply device according to another aspect of the present invention is a DC power supply that supplies DC power, and is connected between the DC power supply and a load, and operates as a unipolar semiconductor device under the control of a control electrode as a switching device. It has a composite function of selecting whether to operate as a bipolar semiconductor element or has a composite function semiconductor element that operates as a unipolar semiconductor element at normal times and operates as a bipolar semiconductor element when instantaneous high power is required. A power converter that converts DC power input from the DC power supply into AC power and outputs the AC power to the load.
The DC power supply includes a rectifier for converting AC of a power system into DC, and a capacitor connected between positive and negative DC output terminals of the rectifier.
The DC power supply is a secondary battery or a fuel cell.
The multifunctional semiconductor device is one of a charge injection type junction field effect transistor (CIJFET) and a charge injection type MOS field effect transistor (CIMOSFET) using silicon carbide (SiC) as a base material. .
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
In the instantaneous large power supply device having the power conversion device using the multifunction semiconductor element as a switching element of the present invention, the multifunction semiconductor element is operated as a unipolar semiconductor element in a normal state, and the instantaneous voltage drop or the load of the apparatus becomes a load. When instantaneous high power is required, such as at the start of operation (at the start of the device), the device is operated as a bipolar semiconductor device. As a result, the power converter operates at the rated power and has low loss during normal times. Although the loss is large at the time of a voltage sag or at the time of starting the device, the device can be operated with power significantly exceeding the rated power.
In particular, a wide-gap semiconductor device using SiC (silicon carbide), GaN (gallium nitride), diamond, or the like as a base material has significantly less loss than a semiconductor device using Si (silicon) as a base material, and operates even at a high temperature. It has the physical property of being able to. Focusing on this point, we investigated the maximum allowable power in a short time that can be controlled by a wide-gap semiconductor device. Turned out not to be. In particular, it was confirmed that the wide-gap bipolar semiconductor device has an “instant large power operation capability” capable of flowing a large current that greatly exceeds the “instant large current supply capability” of the secondary battery.
[0024]
In the power converter (converter) according to the present invention, a wide-gap multifunctional semiconductor element that operates as a unipolar semiconductor element at normal times and operates as a bipolar semiconductor element at the time of instantaneous sag or start-up of an apparatus requiring instantaneous high power is used as a switching element. Normally, the device is operated with a voltage and a current within the rating of the wide gap unipolar semiconductor device. In the event of a voltage sag or start-up of the device, the secondary battery discharges several times the DC power due to the instantaneous large current supply capability of the secondary battery, and operates the multifunction semiconductor device of the converter as a bipolar semiconductor device to convert this DC power into AC power. It converts it to electric power and supplies it to electric heating devices, lighting devices, motor devices, etc.
[0025]
When the voltage of the secondary battery is lower than the voltage of the system bus, the DC output voltage resulting from 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 at “normal time”. When charging the secondary battery, AC power from the system bus is converted into DC power by a converter, stepped down by a chopper circuit, and charged to the secondary battery. The power value that is normally charged and discharged is within the rating of the converter.
[0026]
At the time of an instantaneous voltage drop or an instantaneous power failure, a current several times the rating is supplied while maintaining the rated voltage of the secondary battery substantially 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 the chopper circuit, converted into AC power by the converter, and output to the system bus, thereby stabilizing the power supply.
The converter performs pulse width modulation by performing switching control of a general well-known PWM operation type on the switching element of the multifunction semiconductor element. The output power of this pulse width modulation type converter (hereinafter, referred to as a PWM converter) is advanced from the phase of the voltage of the system bus, and the same power as normal time is output to the system bus, so that the active power is converted to the system bus. Output to the bus is desirable for stable power supply. When the voltage sags, the voltage of the system bus decreases, so the pulse width of the pulse width modulation is increased to operate the converter. As a result, several times the reactive power in the normal state is output to the system bus, and the lowered voltage is quickly returned to the voltage before the instantaneous sag.
[0027]
A wide-cap multifunction semiconductor device for controlling low power, which is made of silicon carbide (SiC) or the like as a base material, can be configured using one semiconductor chip. However, it is difficult to form a wide-gap multifunction semiconductor element for large power control with one semiconductor chip. The reason is that it is difficult to produce a large-area semiconductor chip without any defects because many crystal defects exist in the base material of the wide gap semiconductor element SiC. In particular, it is difficult to produce a chip having a large area through which a large current can flow as in the application of the present invention. If a technology for reducing crystal defects of SiC is improved, a semiconductor element of a chip having a large area equivalent to that of Si can be realized. However, at present, a plurality of chips are connected in parallel to flow a large current.
[0028]
In a conventional converter using a Si bipolar transistor or a Si IGBT provided in a conventional instantaneous large power supply device, the rated capacity of the Si bipolar transistor or the Si IGBT is set to a The capacity must be set to match the power several times the normal power supplied from the battery.
On the other hand, in the instantaneous large power supply device of the present invention, since the SiC CIJFET or the SiC CIMOSFET has a composite function, the converter using this can control a large current several times the rated current. Therefore, even if the converter is set so that the rated current of the multifunction semiconductor element, which is the switching element of the converter, is adjusted to the normal current, it is possible to cope with a large current at the time of a momentary drop. Various components constituting an instantaneous large 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. Further, since the rated capacity is small, the absolute value of the loss is small even at the same conversion efficiency, so that the loss can be reduced and the cost can be significantly reduced. Large converters for power use are required to have higher withstand voltage and higher reliability than small converters. In addition, the price is high because many protection functions are required. For example, in an application where a 5 MW converter is required in a conventional instantaneous large power supply device, the present invention requires only 1 MW. For this reason, the cost is reduced to approximately one fifth of that of the conventional device, and a significant cost reduction can be achieved. The greater the instantaneous large power supply device having a larger power capacity, the greater the effect of cost reduction.
[0029]
Hereinafter, a preferred embodiment of the instantaneous large power supply device of the present invention will be described with reference to FIGS.
<< 1st Example >>
FIG. 1 shows an instantaneous large power supply device 1 for peak cutting according to a first embodiment of the present invention, and important loads 104, 105 and momentary loads from a substation 130 to which the instantaneous large power supply device 1 is connected. It is a block diagram of a power supply system leading to 110. “Peak cut” refers to supplying excess power 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, and in this state Is referred to as “peak cut time”. A state other than the peak cut time 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 loads 104 and 105 are connected to the system bus 102 via respective switches 114 and 115. 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 to maintain the power supply to the important loads 104 and 105 with priority. The instantaneous large power supply device 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 omitted in the drawings because it is well known in the art.
[0030]
The instantaneous large power supply device 1 includes, for example, a secondary battery 2 having a rated voltage of 3.2 kV using a redox flow battery having a rating of 500 kW, a converter 4 having a rating of 500 kW, and a transformer 5 also serving as an interconnection reactor. It is connected to the system bus 102 of 6.6 kV via the unit 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 detection and supply state of power is detected by the detection circuit 8 based on the detected voltage and current. For the voltage detector 10, a potential transformer (PT) or the like is used. The current detector 11 is a current transformer (CT) or the like, and is provided in the substation 130 and detects an output current of the substation 130. The control signal output from the mode switching circuit 13 is input to the control circuit 9 according to the detection output indicating the supply and demand state of the power supplied from the detection circuit 8, and a drive signal corresponding to the control signal is applied to the converter 4 to output power. Control. When the redox flow battery of the secondary battery 2 has a voltage of 800 V, a bidirectional chopper circuit 3 is provided between the secondary battery 2 and the converter 4 as shown in FIG. To 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 type 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, and 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 in consideration of the power loss generated in the chopper circuit 3, the converter 4, and the transformer 5.
[0031]
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 By controlling the converter 4 via the detection circuit 8, the mode switching circuit 13, and the control circuit 9, it is possible to supply active power corresponding to excess power from the secondary battery 2 to the system bus 102 up to a maximum of about 450 kW. The secondary battery 2 is charged by power supplied from the system bus 102 in a steady state in which the supply and demand of power between the substation 130 and the important loads 104 and 105 and the general load 110 is balanced.
[0032]
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 use period, but tends to fall below 800 V as the use period increases. Therefore, at the time of peak cutting, it is desirable that the output voltage of the secondary battery 2 be boosted by the constant voltage output holding type chopper circuit 3 so that the voltage is always kept constant and supplied to the converter 4.
[0033]
The converter 4 that converts DC power into AC power or converts AC power into DC power uses an SiC-CIJFET, which is a multifunctional semiconductor element having SiC as a base material, as a switching element. The converter 4 has a general known circuit configuration and is not shown. It is difficult to increase the current rating of the SiC-CIJFET due to restrictions due to defects in the crystal of SiC. 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 800 V 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. I have. The converter 4 converts the DC power into AC power and applies the AC power 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.
[0034]
When the instantaneous large power supply device 1 is supplying 450 kW peak cut power during peak cut, if a lightning strike occurs in the power system 100, the voltage of the system bus 102 drops instantaneously due to the influence (voltage drop). ) Is detected by the voltage detector 10. The voltage sag may cause the critical loads 104 and 105 to have a serious obstacle such as an operation stop. Therefore, in order to prevent this, the switch 109 is immediately opened and the general load 110 is disconnected. At the same time, in the instantaneous large power supply device 1, the detection output of the voltage detector 10 is input to the detection circuit 8. 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 of operating the SiC-CIJFET of the converter 4 as a unipolar semiconductor element or as a bipolar semiconductor element. The control circuit 9 inputs a PWM control signal for PWM-controlling the SiC-CIJFET, which is a switching element of the converter 4, to the converter 4 according to the input control signal. The control circuit 9 controls the converter 4 so as to output 2.5 MW DC power at a voltage of 800 V, for example, corresponding to the instantaneous large current supply capability from the secondary battery 2. The chopper circuit 3 boosts the DC voltage of 800 V 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 unipolar operation to bipolar operation. As a result, converter 4 outputs active power of 450 kW at a voltage of 1.47 kV and reactive power of 2.78 MVAR (representing the unit of reactive power) at a voltage of about 1.47 kV.
[0035]
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 effect of the lightning strike continues for 0.5 second or more. Since the converter 4 is designed so that the instantaneous large power supply device 1 of the present embodiment can supply 450 kW of active power and a maximum of 2.78 MVAR of reactive power for about 6 seconds, it is sufficient as a measure against instantaneous voltage drop due to lightning. . In the above example, the converter 4 can convert about six times the rated instantaneous high power for four seconds.
In the case where the instantaneous large power supply device of this embodiment is adapted to only the instantaneous voltage drop, only the voltage detector 10 for detecting a voltage may be provided as in the conventional power supply stabilizing device shown in FIG.
[0036]
Next, the SiC-CIJFET of the multifunctional semiconductor device used in the instantaneous large power supply device 1 of the present embodiment will be described in detail. In the present embodiment, the converter 4 can be operated with the power greatly exceeding the rating because the switching element uses the SiC-CIJFET which is a multifunctional semiconductor element.
FIG. 3A is a top view of a SiC-CIJFET device (module) having a rated voltage and a current of 8 kV and 400 A used in the present embodiment, and FIG. It is -b sectional drawing. This SiC-CIJFET device is modularized by connecting nine SiC-CIJFET chips 131 to 139 having a rated current of 45 A in parallel. In FIG. 3B, nine intermediate lower electrodes 16 are provided on the source electrode 14, and nine approximately square CIJFET chips 131 to 139 each having a side of 7 mm are provided on each intermediate lower electrode 16. I have. An intermediate upper electrode 17 is provided on each of the CIJFET chips 131 to 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, the 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 respective CIJFET chips 131 to 139, and define the positions of the respective CIJFET chips 131 to 139 on the cathode electrode 14. The ceramic envelope 19 holds the source electrode 14 and the drain electrode 15 at a fixed distance and insulates them, and has a diameter of about 10 cm.
[0037]
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 form one CIJFET chip. In FIG. 4, the CIJFET cell has an n-type drift layer 51 provided on the upper surface of an n-type SiC substrate 50 functioning as a drain. A p-type buried gate layer 521 is formed in an 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 p-type buried gate layers 522 and 523, respectively, and gate electrodes 57 serving as control electrodes are provided on p-type upper gate layers 524 and 525. The drain electrode 55 is provided on the lower surface of the substrate 50. The p-type buried gate layers 521, 522, 523 and the p-type upper gate layers 524, 525 are electrically connected to the gate terminal 59.
[0038]
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, and the gate voltage applied to the gate electrode 57 as the control electrode is set to the same potential as the source electrode 56, the p-type 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 pinches 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 device 131 operates as a unipolar semiconductor device. 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 flows from the substrate 50 as a drain toward the n-type source layer 54. When the gate voltage is increased, the width of the depletion layer is reduced, and conversely, the width of the channel is increased and a larger current flows.
[0039]
FIG. 5 shows the gate voltage V _G The following shows the voltage-current characteristics between the drain and the source, where is a parameter. As shown in FIG. _G Is 2.5V, the drain-source voltage V _DS Is 4V, the drain-source current I _DS Is 45 A of the rated current. 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, 523 and the p-type upper gate layers 524, 525, and conductivity modulation occurs in the n-type channel layer 53. Therefore, 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 through 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 similarly to 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, the drain-source voltage V _DS Is 4V and the gate voltage V _G Is 4 V, the drain-source current I of 100 A, which is about 2.2 times the rated current, _DS Flows.
[0040]
The operation at the time of peak cutting 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 cutting, 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, and the CIJFET is operated as a unipolar semiconductor element. At the moment of voltage sag, a gate voltage larger than the built-in voltage is applied to operate as a bipolar semiconductor element, and for about 6 seconds, a large current of about 3.5 times that when operating as a unipolar semiconductor element can flow. .
[0041]
An Si-bipolar semiconductor element using silicon (Si) as a base material has a negative temperature dependency in a bipolar operation. Therefore, when a large current flows and the internal temperature of the device rises, the current further increases and the temperature further rises, eventually causing thermal runaway and destruction of the device. When a plurality of Si-Bipolar chips are connected in parallel, once current concentration occurs in a certain Si-Bipolar chip, the current of another Si-Bipolar chip may also be concentrated on that chip, leading to thermal runaway. . Therefore, it is difficult to connect and use a large number of Si-bipolar chips in parallel.
[0042]
On the other hand, the internal resistance of the SiC-CIJFET has a positive temperature dependency. 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 no thermal runaway occurs. If the time during which a large current flows is 10 seconds or less, a large number of SiC-CIJFET chips can be used by connecting them in parallel. The time during which a large current can flow is the time required for the internal temperature of the chip to rise because the amount of heat generated inside each chip is larger than the amount of heat radiation, and to reach the limit temperature at which properties as a semiconductor can be maintained. This time is determined depending on the structure of each chip, the density of the flowing current, the structure of a module in which chips are connected in parallel, and the like. Experiments have shown that the configuration shown in FIG. 3 does not cause any problem for about 6 seconds when a current approximately three times the rated current is passed. For example, a test was performed in which a voltage sag for 8 seconds was generated during the operation test of the peak cut for about 45 minutes, but the peak load and the voltage sag were sufficiently dealt with with little effect on the important loads 104 and 105. The power supply was possible.
[0043]
The converter according to the present embodiment utilizes the instantaneous high power operation capability of the SiC-CIJFET used as a switching element, so that for about 4.5 seconds necessary to prevent the effect of the sag, the converter has about six times the rated power for about 4.5 seconds. Works as a converter to convert power. Therefore, unlike a converter using a conventional silicon semiconductor element, it is not necessary to set the design value of the capacity of the converter to a high power value in consideration of the instantaneous drop. The design value of the capacity is sufficient to be a capacity capable of supplying electric power at the time of peak cut, that is, a capacity capable of supplying electric power that is a fraction of the electric power at the time of an instantaneous drop. As a result, it is possible to significantly reduce the size, weight, and cost of the instantaneous large power supply device capable of responding to the peak cut.
[0044]
<< 2nd Example >>
FIG. 6 is a block diagram of an instantaneous large power supply device 21 for load leveling according to a second embodiment of the present invention. The instantaneous large 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. Similar to the instantaneous large power supply device 1 of FIG. 1, it is connected to the system bus 102 having a voltage of 6.6 KV via the switch 6. Other configurations are the same as those of the instantaneous large power supply device 1. In this embodiment, the instantaneous large power supply 21 functions as a stable power supply for load leveling.
[0045]
"Load leveling" refers to accumulating power during times of low power demand and storing power during times of high demand in order to cope with a phenomenon in which power demand varies significantly depending on time of day. Discharge power. The secondary battery 22 is charged with constant power during the night when power demand is small, for example, 8 hours from 22:00 to 6:00. In the daytime when the power demand is particularly large, for example, for eight hours from 9:00 to 17:00, about 1.35 MW of power is supplied from the secondary battery 22. The switching element (not shown) of the chopper circuit 23 is a SiC-charge injection type MOS field effect transistor (hereinafter, referred to as CIMOSFET) having a voltage and current of 10 kV and 1400 A. The switching element (not shown) of the converter 24 is a SiC-CIMOSFET having a voltage and current of 10 kV and 600 A. It is difficult to produce a SiC-CIMOSFET with a large rated current on one chip, and the current that can flow through one SiC-CIMOSFET chip is about 40A. The SiC-CIMOSFET device (module) used in the converter 22 of the present embodiment is provided with fifteen CIMOSFET chips having a rated current of 40 A in a package similar to that shown in FIG. 3 and connected in parallel to form a module.
[0046]
As described above, since the rated current of the SiC-CIMOSFET is relatively small, the voltage is increased to increase the rated power. For example, when 1.35 MW of power is supplied during the day, the chopper circuit 23 boosts the 1.5 kV DC output voltage of the secondary battery 2 to 3 kV. As a result, DC power having a voltage and current of about 3 kV and 480 A is supplied to converter 4. The converter 24 converts the DC power into AC power having a voltage and current of about 1.38 kV and 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 the boosted voltage to the system bus 102 via the switch 6.
[0047]
When a voltage drop occurs due to a lightning strike in the power system 100 while the 1.35 MW power is being supplied, and the voltage of the system bus 102 is significantly reduced due to the effect, the voltage drop is detected by the 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 the command signal 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 of operating the SiC-CIMOSFET of the converter 4 as a unipolar semiconductor element or as 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 a 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 to the converter 24 a drive signal in which the pulse width of the PWM signal for switching control is enlarged. As a result, the converter 24 outputs active power of about 1.35 MW, which is the rated value, and reactive power of about 6.44 MVAR at a voltage of about 2.07 kV. The output of converter 24 is boosted by transformer 25 and supplied to system bus 102 to prevent a voltage drop of system bus 102.
[0048]
In the instantaneous large power supply device of the present embodiment, the reason why the converter can be operated with power greatly exceeding the rating as described above is that the SiC-CIMOSFET is used as the switching element.
FIG. 7 shows a sectional view of a cell of the SiC-CIMOSFET. The SiC-CIMOSFET has an n-type drift layer 151 formed on a substrate 150 functioning as an n-type SiC drain. 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 regions above the drift layer 151, respectively. The other p-type gate layers 655 and 656 are formed on both the p-type gate layers 653 and 654, respectively. An n-type channel layer 658 is formed in a region surrounded by p-type gate layers 652, 653, and 654. An n-type source layer 659 is formed in a central region above n-type channel layer 658. The drain electrode 160 is provided on the lower surface of the substrate 150, and the 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 the n-type channel layer 658 via MOS gate insulating layers 665 and 666, respectively. The p-type gate layers 652, 653, 654, 655, and 656 are electrically connected to the p-type gate electrodes 661 and 662 and are led out as p-type gate terminals 670. The MOS gate electrodes 667 and 668 are electrically connected and are led out as a MOS gate terminal 673.
[0049]
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 with the drain electrode 160 at a high potential and the source electrode 161 at a low potential and a voltage applied. When the potential is the same as the above, the n-type channel layer 658 is completely covered with the depletion layer around the gate pn junction, and the SiC-CIMOSFET pinches off. As a result, a current does not flow between the drain electrode 160 and the source electrode 161 and a high withstand voltage is obtained. A gate voltage higher than a predetermined threshold value 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 device. That is, the pinch-off due to the depletion layer is eliminated, a channel is formed in the n-type channel layer 658, and current flows from the electron toward the source electrode 161 from the drain electrode 160. When the gate voltage applied to the p-type gate electrodes 661 and 662 is increased, the width of the depletion layer is reduced, and conversely, the width of the channel is increased and a larger current flows between the drain electrode 160 and the source electrode 161.
[0050]
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 device. That is, holes are injected into the n-type channel layer 658 from the p-type gate layers 652, 653, 654, 655, and 656, and conductivity modulation occurs in the n-type channel layer 658, so that the resistance of the n-type channel layer 658 becomes remarkable. Reduce. In addition, electrons are injected into the p-type gate layer 652 from the n-type source layer 659 and the n-type channel layer 658. 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 performs the function of the p-type base, and the CIMOSFET operates as an npn transistor, and a large current due to holes and a large current due to electrons flow from the drain electrode 160 to the source electrode 161.
As the switching elements of the chopper circuit 23 and the converter 24 of the instantaneous large power supply device 21 shown in FIG. 6 of the present embodiment, 15 chips composed of a plurality of cells of SiC-CIMOSFET are connected in parallel, and shown in FIG. A module configured to be similar to the module is used. In the module, the MOS gate electrodes 667 and 668 of the 15 chips are commonly connected, and the p-type gate electrodes 661 and 662 and the p-type gate layer 652 are commonly connected. The drain electrodes 160 of the 15 chips are commonly connected, and the source electrodes 161 are commonly connected.
[0051]
When the instantaneous large power supply device of the present embodiment is used for instantaneous voltage drop, a gate voltage larger than the built-in voltage (about 2.7 kV) of the gate pn junction is applied to the p-type gate electrodes 661 and 662 of the CIMOSFET and the bipolar voltage is applied. Operate as a semiconductor element. If the operation time as a bipolar semiconductor element is about 5 seconds, a large current about 3.8 times that in the case of operating as a unipolar semiconductor element can flow.
In the present embodiment, by utilizing the instantaneous high-power operation capability of the SiC-CIMOSFET, a converter having a rated power of 1.5 MW can be converted to a power of approximately 4.7 times 1.5 MW in a short time to prevent the effect of a sag. The converter can be operated as a converter having a rated power of about 7 MW. Therefore, it is possible to realize an instantaneous large power supply device for load leveling which is significantly reduced in size, weight, and cost and can cope with an instantaneous voltage drop.
[0052]
<< 3rd Example >>
A third embodiment of the present invention will be described with reference to FIG.
FIG. 8 is a block diagram showing an example in which the instantaneous large power supply device of the present invention is applied to a 100 kW, 500 Hz class induction heating device. Heating equipment for rapidly heat-treating metal parts under high-precision temperature control requires that a low-temperature heating furnace be quickly heated to a predetermined high temperature at the start of operation or during operation, or conversely a high-temperature heating furnace. Need to be rapidly brought to a predetermined low temperature. In particular, at the start of operation, a larger amount of electric power is required than when a predetermined high temperature is maintained in a steady operation state.
[0053]
In FIG. 8, a rectifier 301 is connected to a three-phase power distribution system line 290 via a switch 292, and an input three-phase AC is rectified to obtain a DC output at DC 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 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, respectively. A temperature sensor 306 for detecting the temperature in the heating furnace is provided near the heating coil 304, and a detection output is input to a detection circuit 309. Current detectors 307 and 308 such as CTs are provided on two of the three-phase input lines of the rectifier 301, and detection outputs are input to a detection circuit 309.
[0054]
A current detector 305 is also provided on an output line connected to the output terminal 315 of the inverter 303, and a detection output is input to a 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 of operating the switching elements 331 to 334 as unipolar semiconductor elements or operating as switching elements, and inputs a mode control signal to the control circuit 310. Four output terminals of the control circuit 310 are connected to respective 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, 314 are connected to the gates of the switching elements 331, 332, 333, 334, respectively. A well-known diode for flywheeling is connected between the source and the drain of each of the switching elements 331 to 334.
In the inverter 303, the switching elements 331, 332, 333, and 334 are configured by a CIJFET module having a rated voltage and current of 1 kV and 150 A. The configuration of the CIJFET module is similar to that of the first embodiment shown in FIG. The inverter 303 converts a DC output of the rectifier 301 into an AC output, and supplies the AC output to the induction heating coil 304 via the capacitors 317 and 318.
[0055]
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 that determines 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 of the drive circuits 311 to 314 generates a drive signal for each of the switching elements 331 to 334 based on the input control signal, and applies the drive signal to each of the switching elements.
[0056]
The induction heating device needs to raise the temperature in the heating furnace to a predetermined temperature within a predetermined time (for example, 5 to 30 seconds) depending on the material, shape, and purpose of use of the metal component to be heat-treated. Therefore, it is usually necessary to supply a large amount of electric power when starting the operation of the induction heating device. In the present 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 of 3 to 5 times the steady state is supplied to the heating coil 304. Can be supplied to In a steady state, it is desirable to operate the CIJFET as a unipolar semiconductor element to prevent power loss in the CIJFET. If a large-capacity capacitor is used as the capacitor 302, when the power supplied to the heating coil 304 increases rapidly, the electric charge charged in the capacitor 302 compensates for the sudden increase in the supplied power. As a result, it is possible to prevent a drop in the voltage of the distribution system line 290 due to a sudden increase in the supplied power.
[0057]
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 at the time of steady operation, and when a large output is required in a short time such as at the start of operation or at the time of rapid heating, By operating the CIJFETs of the switching elements 331 to 334 as bipolar semiconductor elements, it is possible to obtain an output that is three to five times the normal state. Therefore, the size, weight, and cost of the induction heating device can be reduced.
[0058]
<< 4th Example >>
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 the alternating current applied to the traveling motor 404 is, for example, 18 kHz.
[0059]
In FIG. 9, a three-phase inverter 403 as a power converter 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 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 near a shaft connected to the rotor, and a detection signal representing the rotation speed of the shaft is input to a detection circuit 408. The stator current of the motor 404 is detected by a current detector 420 such as a CT, and a detection signal is input to a 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 processed signal to the mode switching circuit 410. The mode switching circuit 410 applies a mode control signal for determining an operation mode of the switching elements 431 to 436 to the inverter control circuit 409. The control circuit 409 outputs a control signal to each of the drive circuits 421, 422, 423, 424, 425, 426 for driving the switching elements 431, 432, 433, 434, 435, 436 of the inverter 403. The drive circuits 421 to 426 apply drive signals for driving the switching elements 431 to 436 to gates that are control electrodes of the switching elements 431 to 436 based on the input control signals. A diode for flywheeling is connected between the source and the drain of each of the switching elements 431 to 436.
[0060]
As the switching elements 431 to 436 of the inverter 403 in the instantaneous large power supply device of the present embodiment, the CIMOSFET module shown in FIG. 7 and described in the second embodiment is used.
In an electric vehicle, when the vehicle suddenly starts, or when the tire escapes when the tire enters a mud, the electric power needs to be supplied to the motor 404 for a short time, but several times as much as that in normal traveling. The switching elements 431 to 436 of the inverter 403 in the present embodiment are, for example, CIMOSFET modules having a rated voltage and a current of 1 kV / 600 A class. When a large electric power needs to be supplied to the motor 404 at the time of starting or accelerating the electric vehicle, the corresponding processing signal of the detection circuit 408 is input to the mode switching circuit 410, and the corresponding mode control signal is supplied to the inverter control circuit. 409. 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 control electrodes of the CIMOSFET element shown in FIG. The voltage value is, for example, 5 to 30 V for the MOS gate voltage and 2.7 to 25 V for the p-type gate voltage. As a result, the CIMOSFET device operates as a bipolar semiconductor device, and the inverter 403 can supply the motor 404 with AC power of about 1.5 to 4 times the rated power. The time during 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 battery 401 of the secondary battery and the fuel cell for an automobile can supply several times the rated power for a short time.
[0061]
During normal running 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 device operates as a unipolar semiconductor device.
In a conventional inverter having a switching element using silicon, it is necessary to configure the inverter using a switching element having a rated power of 1.5 to 4 times the rated output. By using a multifunctional semiconductor device capable of selecting an operation and a bipolar operation, it is possible to cope with a large power several times the rated power by using an inverter having a rated power substantially equal to the output power during normal running. As a result, the size, weight and cost of the inverter for the electric vehicle can be significantly reduced.
[0062]
As described above, 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 made.
For example, the multifunctional semiconductor element of the switching element is not limited to CIJFET or CIMOSFET. Also, semiconductor elements made of a wide gap semiconductor material other than SiC, such as gallium nitride or diamond, can be used for the converter, the inverter, and the like. Also, a multifunctional element made of Si can be used. The multifunctional semiconductor device can also be used as a switching device of a switching power supply.
[0063]
The battery may be a zinc chloride battery, a zinc bromine battery, a lithium ion battery, or the like, in addition to a redox flow battery, a sodium sulfur battery, a lead battery, a fuel cell, and the like.
In the case of an instantaneous large power supply device having a small power capacity of 200 kW or less, the current capacity is small, so that a wide-gap bipolar semiconductor element having a small chip area can be sufficiently used. In this case, it is not always necessary to provide a chopper circuit for boosting the voltage in order to obtain a predetermined power with a small current, and the output of the battery may be directly applied to a power converter such as an inverter.
[0064]
A wide gap bipolar semiconductor device having a high breakdown voltage can be easily realized. For example, in the first and second embodiments, a high withstand voltage of 20 kV or more enables direct connection to the 6.6 kV system bus 102. Therefore, it is also possible to use only the interconnection 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, the components constituting the instantaneous large power supply device are set to a high withstand voltage and large current, so that the power system can be further upstream. It can also be applied to an instantaneous large power supply device to be connected. Also, the instantaneous high power of the present invention can be applied to a relatively long-term `` instantaneous power outage '' of more than a few minutes when a small animal such as a snake or a bird is caught on the transmission line or a tree touches and a short circuit or ground fault occurs. A feeding device can be applied. Further, when one of the plurality of generators of the power transmission power supply fails or the load of a large power consumer (such as a factory) suddenly stops operating, a sudden fluctuation in power occurs, and the imbalance in power supply and demand becomes 5%. May last more than a minute. For example, increase the capacity of the secondary battery and cool down the switching elements even if the system frequency fluctuates due to imbalance between the power supply and demand for 5 minutes to 1 hour, which is much longer than the duration (several seconds) of the sag due to lightning. By taking measures to keep the temperature below a predetermined value, the instantaneous large power supply device of the present invention can be applied. In such a long time, the instantaneous large power supply device of the present invention can adjust the power of about 1.5 to 3 times the rated output, and can be used as an emergency electric wire.
[0065]
【The invention's effect】
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 multifunctional semiconductor element in which one of a unipolar operation and a bipolar operation is selected, and the output is At the time of normal operation below the rated power, a unipolar operation is performed. When instantaneous high power is required, the multifunction semiconductor device is operated in a bipolar manner so that power exceeding the rated power in normal operation can be controlled. As a result, an effect is obtained that the instantaneous large power supply device can be significantly reduced in size, weight, and cost.
[Brief description of the drawings]
FIG. 1 is a block diagram of an instantaneous large power supply device for peak cutting according to a first embodiment of the present invention.
FIG. 2 is a block diagram of another example of an instantaneous large power supply device for peak cutting according to the first embodiment of the present invention;
FIG. 3A is a plan view of a SiC-CIJFET module used in the converter of the first embodiment.
(B) is a bb sectional view of (a).
FIG. 4 is a cross-sectional view of a SiC-CIJFET cell.
FIG. 5 is a graph showing a drain-source voltage-current characteristic of a SiC-CIJFET with a gate voltage as a parameter.
FIG. 6 is a block diagram of an instantaneous large power supply device for load leveling according to a 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 large power supply device for induction heating according to a third embodiment of the present invention.
FIG. 9 is a block diagram of an instantaneous large power supply device for a traveling motor of an electric vehicle according to a fourth embodiment of the present invention.
FIG. 10 is a block diagram of a conventional peak cut power stabilizing device.
[Explanation of symbols]
1,21 Instantaneous large power supply device
100 power grid
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 electrode
311 to 314, 421 to 426 Drive circuit
331-334, 431-436 Switching element
303, 403 Inverter

Claims (19)

A secondary battery that charges and discharges DC power, and the secondary battery, connected between the system bus of the power transmission power supply, as a switching element, operated as a unipolar semiconductor element by control by a control electrode or as a bipolar semiconductor element A multifunction semiconductor device having a multifunction that is selected to be operated is provided, and the alternating current input from the system bus is converted to direct current and output to the secondary battery, and the direct current output from the secondary battery is output. An instantaneous large power supply device having a converter, which is a power conversion device that converts the power into an alternating current and outputs the converted power to the system bus. A secondary battery that charges and discharges DC power, and the secondary battery, connected between the system bus of the power transmission power supply, as a switching element, operated as a unipolar semiconductor element by control by a control electrode or as a bipolar semiconductor element It has a composite function that is selected to be operated, has a wide-gap composite function semiconductor element that normally operates as a unipolar semiconductor element when normally operated, and operates as a bipolar semiconductor element when instantaneous high power is required, and from the system bus Instantaneous high power having a converter which is a power conversion device that converts an input AC into a DC and outputs the DC to the secondary battery and converts a DC output from the secondary battery into an AC and outputs the AC to the system bus. Feeding device. Rechargeable battery that charges and discharges DC power,
A bidirectional chopper circuit that is connected to the secondary battery, reduces a charging voltage of the secondary battery, and increases a discharge voltage of the secondary battery;
A wide gap that is connected between the chopper circuit and the system bus of the power transmission power supply and has a composite function of selecting whether to operate as a unipolar semiconductor element or a bipolar semiconductor element under control of a control electrode as a switching element. A power conversion device comprising a multifunction semiconductor element, converting AC input from the system bus into DC and outputting the DC to a chopper circuit, and converting DC input from the chopper circuit into AC and outputting the AC to the system bus. A converter,
A detection device that detects a voltage of the system bus, and a detection device that detects a power supply and demand state based on the detected voltage; and, based on a detection output of the detection device, a load and a power transmission power supply connected to the system bus. When the supply and demand of power are balanced, the control circuit controls the converter to charge the secondary battery and to discharge the secondary battery and supply the power to the system bus when the demand exceeds the supply. Instantaneous large power supply device. Rechargeable battery that charges and discharges DC power,
A bidirectional chopper circuit that is connected to the secondary battery, reduces a charging voltage of the secondary battery, and increases a discharge voltage of the secondary battery;
A wide circuit which is connected between the chopper circuit and a system bus of a power transmission power supply and has a composite function of selecting whether to operate as a unipolar semiconductor element or to operate as a bipolar semiconductor element as a switching element by control of a control electrode. A power conversion unit that includes a gap composite function semiconductor element, converts AC input from the system bus to DC, outputs the DC to a chopper circuit, converts DC input from the chopper circuit to AC, and outputs the AC to the system bus. A converter that is a device, a detection device that detects a voltage and a current of the system bus, and a detection device that detects a power supply / demand state 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 the load and the power transmission power supply are balanced, the secondary battery is charged, When needed exceeds the supply, the instantaneous large power supply device having a control circuit for controlling the converter such that by discharging the secondary battery to supply power to the system bus. At the time of an instantaneous voltage drop in which the voltage of the system bus is greatly reduced for a short time due to the occurrence of a lightning accident or the like, the secondary battery outputs discharge power twice to 12 times the rated discharge power of the secondary battery,
The converter converts discharge power of the secondary battery, which corresponds to twice to twelve times the rated control power of the converter, into alternating current, and supplies predetermined reactive power and active power of two to twelve times the rated power to the system bus. 5. The instantaneous large power supply device according to claim 3, wherein the power is controlled by the control circuit so as to output the power. At the time of an instantaneous voltage drop in which the voltage of the system bus is greatly reduced for a short time due to the occurrence of a lightning accident or the like, the secondary battery outputs discharge power twice to 12 times the rated discharge power of the secondary battery,
The converter converts discharge power of the secondary battery corresponding to twice to twelve times the rated control power of the converter into AC and outputs predetermined reactive power and active power smaller than twice the rated power to a system bus. The instantaneous large power supply device according to claim 3, wherein the instantaneous large power supply device is controlled by the control circuit so as to perform the control. The instantaneous large power supply device according to any one of claims 1 to 6, wherein an interconnection reactor is provided between the system bus and the converter. The instantaneous large power supply device according to claim 1, wherein the secondary battery is one of a redox flow battery and a sodium sulfur battery. 5. The instantaneous light emitting device according to claim 1, wherein the wide gap composite function semiconductor device is a charge injection type junction field effect transistor (CIJFET) based on silicon carbide (SiC). Power supply. 5. The instantaneous high power supply device according to claim 1, wherein the wide gap composite function semiconductor device is a semiconductor device using gallium nitride as a base material. 6. 5. The instantaneous large-scale semiconductor device according to claim 1, wherein the wide-gap multifunction semiconductor device is formed by connecting at least one chip or a plurality of chips of a SiC CIJFET in parallel. Power supply. 5. The instantaneous large-scale semiconductor device according to claim 1, wherein the wide-gap multifunction semiconductor device is formed by connecting at least one chip or a plurality of chips of a SiC CIMOSFET in parallel. Power supply. Rechargeable battery that charges and discharges DC power,
A bidirectional chopper circuit that is connected to the secondary battery, reduces a charging voltage of the secondary battery, and increases a discharge voltage of the secondary battery;
A wide gap that is connected between the chopper circuit and the system bus of the power transmission power supply and has a composite function of selecting whether to operate as a unipolar semiconductor element or a bipolar semiconductor element under control of a control electrode as a switching element. A power conversion device comprising a multifunction semiconductor element, converting AC input from the system bus into DC and outputting the DC to a chopper circuit, and converting DC input from the chopper circuit into AC and outputting the AC to the system bus. A converter,
A detecting device that detects a frequency of the system bus, and detects a power supply / demand state based on the detected frequency, and a load and a power transmission power supply connected to the system bus based on a detection output of the detecting device. When the supply and demand of power are balanced, the control circuit controls the converter to charge the secondary battery and to discharge the secondary battery and supply the power to the system bus when the demand exceeds the supply. Instantaneous large power supply device. A secondary battery that charges and discharges DC power, and is connected between the secondary battery and a load connected to a system bus of a power transmission power supply, and operates as a switching element and as a unipolar semiconductor element under the control of a control electrode. Or a wide-gap multifunction semiconductor element having a multifunction selected to operate as a bipolar semiconductor element, converting AC input from the system bus into DC and outputting the DC to the secondary battery, An instantaneous large power supply device having a converter, which is a power conversion device that converts DC output from a battery into AC and outputs the AC to the load. A detection device that detects a voltage and a current of power supplied to the load connected to the system bus, and detects a supply and demand state of the power of the load based on the detected voltage and current; and a detection output of the detection device. Based on, when the supply and demand of the power of the load and the power transmission power supply are balanced, the secondary battery is charged, and when the demand exceeds the supply, the secondary battery is discharged and the power is supplied to the system bus. The instantaneous high power supply device according to claim 14, further comprising a control circuit that controls the converter to supply the power. A DC power supply that supplies DC power, and a composite function that is connected between the DC power supply and a load and that selects whether to operate as a unipolar semiconductor element or a bipolar semiconductor element as a switching element under control of a control electrode. Having a multifunctional semiconductor element that normally operates as a unipolar semiconductor element and operates as a bipolar semiconductor element when instantaneous high power is required, and converts DC power input from the DC power supply into AC power. An instantaneous large power supply device comprising a power conversion device for converting and outputting the converted power to the load. 17. The instantaneous large power supply device according to claim 16, wherein the DC power supply includes a rectifier that converts AC of a power system into DC, and a capacitor connected between the positive and negative DC output terminals of the rectifier. . 17. The instantaneous large power supply device according to claim 16, wherein the DC power supply is a secondary battery or a fuel cell. The composite function semiconductor device is one of a charge injection type junction field effect transistor (CIJFET) and a charge injection type MOS field effect transistor (CIMOSFET) using silicon carbide (SiC) as a base material. The instantaneous large power supply device according to claim 16.

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