JP2018195547A - Opening/closing device for dc power system - Google Patents

Abstract

To eliminate leakage current and increase withstanding voltage of a hybrid switch configured by parallel-connecting a semiconductor switch and a metal contact switch, and that uses a metal contact for energization and uses the semiconductor switch for cutoff.SOLUTION: An opening/closing device uses a triple metal contact. For opening the contact, a conduction contact is opened first, and then, a next contact is opened to turn off a gate of a semiconductor switch, and at that time the conduction contact is in an open distance state that withstands a restriking voltage, and thereafter, a last contact is opened to disconnect a semiconductor switch circuit, and all contacts are in an open state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a DC power system switchgear, which is energized by a metal contact, and interrupted by a semiconductor switch, so-called a hybrid switch. The present invention relates to an open / close device capable of safely opening / closing a direct current of a voltage source such as a power source or a high voltage secondary battery, or a DC power facility such as an electric vehicle, a smart house, or a smart grid.

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct current switchgear and relates to a metal contact and a semiconductor switch that are continuously energized by a metal contact switch having a low conduction loss, although the direct current is interrupted by a semiconductor switch in order to interrupt the direct current without arcing The present invention relates to a hybrid switchgear that uses both.

  In recent years, with the advancement of semiconductor switches, power MOSFETs and IGBTs with insulated gates can be turned on and off at high voltages and large currents, but semiconductor devices are still energized compared to metal contacts. The electric resistance is large, heat is generated, and a large cooling device is required for continuous energization. On the other hand, if the interruption of the direct current of about 10 A or more is performed by opening the metal contact, the electric current is not interrupted but arc discharge occurs and the current continues. Since the contact metal is melted and consumed by the high-temperature arc plasma generated at the time of opening, the current cannot be interrupted unless the arc is extinguished in a short time. For example, in order to extinguish the arc, there is a method in which the arc length is extended by magnetism and the arc is extinguished by cooling, but the electrode is consumed by the arc and the life of the contact is shortened.

  In recent years, silicon carbide semiconductors have been put into practical use, and high-withstand-voltage semiconductor switches of several kV are being put into practical use in MOSFETs (Metal Oxide Field Effect Effect Transistors). Using this high-breakdown-voltage semiconductor switch, it has become possible to provide a high-voltage DC power system switch without arc, which has been difficult with metal contacts. However, the energization loss of the semiconductor switch is still larger than that of the metal contact, and the continuous energization requires a cooling device for the semiconductor switch, resulting in a large size. Therefore, by combining both advantages, a hybrid arc-free switch and circuit breaker are desired which are energized with a metal contact and energized with a semiconductor switch only at the time of interruption.

  The arc-free switch according to the present invention disclosed in Japanese Patent No. 5864006 improves the problem of surge withstand voltage determined by the leakage current in the open state and the withstand voltage of the semiconductor switch.

Patent 5864006 "DC power system safety device" Japanese Patent Application No. 2015-199768 “Restart Voltage Control Device”

The Electrotechnical Society "Discharge Handbook" Part 2 Chapter 6 Arc Discharge

  The good point of the mechanical metal contact is that the on-resistance when energized is negligibly small and it is not necessary to consider heat generation. Conversely, the insulation resistance when off is generally said that there is no conduction, that is, leakage. It is recognized that there is no current. Further, the withstand voltage at the OFF time is expected to have a discharge breakdown voltage of about 3 kV with an opening distance of 1 mm. The hybrid switching circuit in which the mechanical contact and the semiconductor switch shown in Prior Patent Document 1 are in parallel is as expected when turned on, but the insulation resistance and withstand voltage when turned off are limited to the leakage current and withstand voltage of the semiconductor switch circuit. Is done. I think that this is not enough and hinders the spread and trust of hybrid switches.

  In the prior art document 1, the control of the semiconductor switch turns off the semiconductor switch by turning on the b contact of the mechanical contact, but the mechanical metal contact is repeatedly turned on / off by rebounding or sliding of the contact when turned on. So-called chattering may occur, and there is a problem that the semiconductor switch is repeatedly turned on and off. Although it was a countermeasure, in the prior art document 2, it is possible to prevent repeated ON / OFF many times by configuring a Miller integrating circuit using a semiconductor switch, but there is a disadvantage that Joule loss of the semiconductor switch increases. there were.

    The present invention has been made in view of the above two points, and an object of the present invention is to add a series switch to a conventional hybrid switch so that the insulation resistance when OFF is the same as that of a general switch, and a semiconductor switch Ensuring a sufficient electrode distance when shutting off, and mechanical contact off, there is no chattering, or even if it is less frequent, it can be solved by turning off the semiconductor switch by turning off the control contact. It is an object of the present invention to provide means for reliably realizing these by the arrangement and driving method of three contact electrodes, not by a sequence or a time delay control method.

Means to solve the problem

  In order to achieve the above object, the electrode structure or the arrangement of the triple contacts is performed. However, an opening distance is provided, and d1 is a time required for shutting off the semiconductor switch = (d1 / speed V), tens of micro S However, d2 is set so as to secure an opening distance that can withstand a re-emergence voltage generated after the semiconductor switch is shut off.

Effect of the invention

  Thus, by making the metal contact a triple switch having an opening distance of d1 and d2, the opening distance necessary for the control timing of the semiconductor switch and the withstand voltage against the surge voltage during the opening operation. Is achieved, and an arc-free DC switchgear with no leakage current is realized.

  The DC current switchgear with such a configuration can reliably obtain time timing and insulation distance at the time of opening, so even a simple operation electromagnetic drive, manual operation, uncertain operation such as limit switch, etc. A reliable DC switch can be realized.

It is explanatory drawing which showed the implementation method of the switch apparatus of the DC power type | system | group which concerns on this invention. It is the circuit diagram which showed the method in the case of the electric current 1 direction of the switch apparatus of the DC power system which concerns on this invention. (Example 1) It is circuit explanatory drawing of the switchgear in the case of current bidirectional | two-way based on this invention. (Example 2) It is a figure explaining the electrode structure of an electromagnetic drive type triple contact. The operation at the time of closing of the sequential drive type triple contact is shown in a schematic view. (1) A photograph of changing the distance between the fixed electrodes of a three-pole electromagnetic switch, and (2) waveforms of a semiconductor current, a regenerated voltage, and a gate voltage of a SiC-MOSFET when a direct current is interrupted.

As shown in FIG. 1, in a triple switch that collectively drives three metal contacts, if the electrode spacing is different and the distance between the electrodes is the shortest S1, the largest S3, and the middle S2, the distance is short. The contacts are sequentially turned on in the order of S1, S2, and S3 from the contact points, and the opening is turned off in the order of S3, S2, and S1.
The three contacts are opened and closed in one operation, but the contact between the movable electrode and the fixed electrode is made different so that the three contacts are opened and closed sequentially. S1), the next contact to be closed is the control contact (S2), the last contact to be closed is the energization contact (S3), and when opening the three switches that are sequentially opened in the reverse sequence Using a contact, a semiconductor switch is connected to S1 and connected in parallel with a conduction contact (S3) that becomes a main contact for connecting a power source and a load. By an ON / OFF signal of the control contact (S2) or its current The gate of the semiconductor switch (MOSFET) is turned on / off.

  When the movable electrode starts to move from the closed position and S3 is turned off, S1 and S2 are still in the on state, the semiconductor switch is in the on state, and the current of the metal contact S3 becomes a discharge arc at the moment of opening. Will continue to flow between the poles. When a metal electrode is opened while a current is flowing, arc discharge occurs. However, according to Non-Patent Document 1, a very short arc voltage-current characteristic has been reported for a contact arc. The contact arc has a minimum arc voltage Vmin and a minimum arc current Imin, and has a minimum voltage and current to maintain the cathode spot (cathode spot) on the electrode for generating the arc. The voltage between them varies depending on the contact metal, but in the range of 10V to 20V, the minimum arc voltage Vmin does not change with current, but it is reported that the contact arc voltage increases as the arc length increases.

遮断電流Ｉを１００Ａ、スイッチ回路のインダクタンスＬを数十ｎＨ、とすると転流時間Ｔ＝１０ｎＳのオーダーである。回路インダクタンスが小さいため、電流は瞬時に半導体スイッチに移り、最小アーク電流以下になってアークは消滅するので、発生しないか、発生しても１０ｎＳのマイクロ・アークとなって、観測も難しい。When S3 is opened, the semiconductor switch is on, so the semiconductor on-voltage is several volts. Approximate time T required for commutation from S3 to S1

When the cut-off current I is 100 A and the inductance L of the switch circuit is several tens of nH, the commutation time T is on the order of 10 nS. Since the circuit inductance is small, the current instantaneously moves to the semiconductor switch, and the arc disappears when the current is less than the minimum arc current. Therefore, even if it occurs, it becomes a 10 nS micro arc, and observation is difficult.

数ＫＶの耐電圧が期待される場合でもｄ２は１ｍｍ程度あれば十分である。When the electrode interval of S3 becomes d2, S2 is turned off, the semiconductor switch is turned off, the current is interrupted, and a regenerative voltage is generated. At this time, the electrode interval of S3 is d2, and since it has a dielectric strength of about 3 kV / mm in the air, the withstand voltage between the electrodes needs to be equal to or higher than the regenerative voltage.

Even when a withstand voltage of several KV is expected, d2 of about 1 mm is sufficient.

FIG. 1 is a basic configuration diagram of an embodiment of the present invention.
A procedure for opening without causing an arc from a closed state where a direct current flows will be described.
The metal contact S3 through which current flows is opened first, but at that time, S2 and S1 are in the on state, and the gate power supply is connected to the gate, so that the semiconductor switch is in the saturated state. The energizing current is commutated to the semiconductor switch at several tens of nS after the opening of S3. Eventually, when S2 is also turned off, the gate voltage becomes zero and the semiconductor switch cuts off the current. Although a regenerative voltage is generated, the opening interval of S3 is d2, and there is no fear of dielectric breakdown. Finally, S1 is opened, but there is no current in the semiconductor switch, and S1 is opened when there is no current.
That is, if the triple switching mechanism shown in FIG. 1 is used in a hybrid switch composed of a metal contact with little conduction loss at the time of closing and a semiconductor switch capable of interrupting current by gate voltage control, the opening can be performed without generating a DC current arc. And leakage current at the time of opening can be eliminated.

First Embodiment: FIG. 2 and claim 2 are basic circuit diagrams of an embodiment of the present invention, which can be realized with a minimum number of parts, and a direct current is opened without generating an arc. MOSFET: 2 can cut off the current.
The opening procedure will be described.
The metal contact S3 through which the current flows is opened first. At that time, the S2 is in the ON state, the resistance R1: 4 is several tens kΩ here, the gate resistance Rg: 5 is several hundred kΩ, and the constant voltage diode is six. Since it is connected to the gate, the semiconductor switch is turned on in a saturated state by the voltage of the constant voltage diode (here, 12 V). Here, since the semiconductor switch needs to have a low on-voltage, any semiconductor switch having an insulated gate structure such as a MOSFET having a low on-resistance or an IGBT having a low on-voltage may be used. The energizing current is commutated to the semiconductor switch at several tens of nS after the opening of S3. Eventually, when S2 is also turned off, the gate voltage becomes zero by the resistor Rg, and the semiconductor switch cuts off the current. Although a regenerative voltage is generated, the opening interval of S3 is d2, and there is no fear of dielectric breakdown. Finally, S1 is opened, but there is no current in the semiconductor switch, and S1 is opened when there is no current.
When the opening is finished, there is no leakage current due to the air layer, and the surge voltage can withstand the withstand voltage determined by the electrode spacing.

  2nd Embodiment: FIG. 3 and claim 3 are the semiconductor circuit contact (S1) connected in parallel with the conduction contact (S3) through the AC terminal of the diode bridge: 7, and the DC terminal of the diode bridge The drain of the semiconductor switch (MOSFET: 2) is connected to the plus, the source terminal is connected to the minus terminal, and the semiconductor switch (MOSFET) is turned on / off by the ON / OFF signal of the control contact (S2).

[Embodiment 1 of electrode structure: FIG. 4]
FIG. 4 is an explanatory diagram of the structure of the direct current connection device according to the embodiment of the present invention.
The movable electrode collectively drives the three contacts to contact the fixed electrode. As shown in FIG. 4, the electrode interval S2 is longer than S1 by d1, and S3 is longer than S2 by d2. Is set to The contacts of S1, S2, and S3 are sequentially opened or closed by being manually or mechanically driven by a cam or the like. In this example, during the opening operation, after S3 is turned off, the regenerated voltage is generated when S2 is turned off, and it is necessary that the withstand voltage of S3 already opened is sufficient. There is a gap in.

[Embodiment 2: Electrode Structure: FIG. 5]
FIG. 5 is a schematic diagram showing the circuit configuration of the first embodiment of the present invention, the circuit configuration of claim 2, and the DC current connection device of FIG. ing.
(1) shows the conductive state of the metal contacts when S1, S2 and S3 are all on. Even if the gate voltage is on, almost no current flows through the semiconductor switch.
In (2), S3 is turned off. At this time, since S2 and S1 are on, the voltage of S3 is the sum of the ON voltage of the semiconductor switch and the forward voltage of the diode bridge, which is the contact arc voltage. Lower, the current commutates to the S1 semiconductor switch circuit.
When S2 is turned off in (3), the semiconductor switch is turned off, a re-emergence voltage is generated, and the current is interrupted. At this time, it is necessary that the opening interval d2 withstands this re-induced voltage.
In (4), since the semiconductor switch circuit also has zero current, S1 is released without arcing.
Eventually, from (1) to (4), the arc is closed and opened.

[Electromagnetic switchgear and voltage / current waveform: Fig. 6]
FIG. 6 (1) shows an embodiment of the electrode structure according to the first embodiment of the present invention shown in FIG.
The fixed electrodes S1, S2, and S3 change the distance between the electrodes by d1 and d2, respectively. d1 was about 0.5 mm, d2 was about 1 mm, and the time difference for turning off was 1.2 mS for S3-S2 and 0.5 mS for S2-S1.
(2) is a current waveform at the time of interruption, a gate voltage of the SiC-MOSFET, and a re-emergence voltage waveform. When S3 is turned off, the current is commutated to the semiconductor switch and the current starts to flow, which is 7A here. S2 is turned off, the gate voltage is lowered, the semiconductor current is cut off, and a re-starting voltage is generated. In the experiment, it is a semiconductor switch of SiC (silicon carbide) -MOSFET (1.2 kV, 5 A), but it turns off without any problem at a regenerative voltage exceeding 800 V, and the opening proceeds without breaking down at the electrode distance of d2. , S1 is turned off with no current.

Highly reliable current switching devices for safety are required. The present invention is a hybrid switch that uses a mechanical contact as a current-carrying contact for direct current switching, and there is a disconnection with an air layer so that there is no leakage current when the switch is off and withstands surge voltage.
In this way, the hybrid switch between the semiconductor switch and the mechanical contact extends the switching life of the switch because it is not melted or broken by an arc, and provides a DC current switch that can be used with manual or limit switch drive mechanisms that have been difficult until now. can do.

  Since the switchgear of the present invention solves various problems of DC power switchgear and has improved durability and reliability, the application of DC power such as solar power generation, battery storage, DC power distribution, and electric vehicles will further advance. Conceivable.

1: DC power supply 2: MOSFET
3: Triple opening / closing mechanism 4: Resistance R1
5: Gate resistance Rg
6: Zener Diode (constant voltage diode)
7: Diode bridge

Claims (5)

A direct current switch, the switchgear having three metal contacts;
The first contact and conduction contact (S3) are inserted between the power source and the load to form a continuous energization switch, and the second contact and semiconductor circuit contact (S1) are connected to the previous conduction through the semiconductor switch circuit. Connected in parallel with the contact S3, the third contact, the control contact (S2) is a gate control contact for performing on / off control of the semiconductor switch circuit by turning on or off,
When closing the contacts S1, S2, and S3 of the three metal contacts, the contacts are sequentially turned on in the order of S1, S2, and S3. When the contacts are opened, the contacts are sequentially turned off in the order of S3, S2, and S1. A switchgear characterized in that, when S2 is turned off, the inter-electrode distance d2 of the conducting contact S3 is an electrode interval that does not cause dielectric breakdown with respect to the regenerated voltage after the current interruption.   When the direct current direction is one direction, an insulated gate semiconductor switch is connected to the semiconductor circuit contact (S1), and the gate drive voltage is obtained by dividing the voltage from the direct current power source by turning on the control contact S2. The switchgear described in 1.   The semiconductor circuit contact (S1) is connected in parallel with the conduction contact (S3) via the AC terminal of the diode bridge, the drain of the semiconductor switch (MOSFET) is connected to the positive terminal of the diode bridge, and the negative terminal The switchgear according to claim 1, wherein source terminals are connected to each other, and the semiconductor switch is on / off controlled by an on / off signal of the control contact (S 2).   The semiconductor circuit contact (S1), the control contact (S2), and the conduction contact (S3) are three-pole electromagnetically driven switches. The distance between the electrodes is d1 and d2, respectively. The switchgear according to any one of claims 1, 2, and 3, wherein the electrode spacing does not cause dielectric breakdown.   The semiconductor circuit contact (S1), the control contact (S2), and the conduction contact (S3) are manually driven or mechanically driven, but are inserted in the order of S1, S2, and S3, and released in the order of S3, S2, and S1, but S2 is The switchgear according to any one of claims 1, 2, and 3, wherein the opening interval of S3 is in a state that can withstand a regenerated voltage at the time of turning off.

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