JP4044533B2 - Switching device - Google Patents

Description

  The present invention relates to a switching device that switches a switching circuit such as a voltage compensation circuit that compensates for a voltage fluctuation supplied to a load and a mechanical relay connected in parallel to the switching circuit.

The voltage of the electric power system is instantaneously reduced by lightning, etc., and precision equipment such as factories malfunctions or is temporarily stopped, which can cause great damage on the production line. In order to prevent such damage, a voltage fluctuation compensator that monitors voltage fluctuations such as an instantaneous voltage drop (hereinafter referred to as a momentary voltage drop) of the power system and compensates for the voltage drop is used.
A conventional voltage fluctuation compensator is configured by a plurality of voltage compensation circuits that are connected in series to a power system and output a compensation voltage with either positive or negative polarity. Each voltage compensation circuit is provided with a full bridge inverter composed of four semiconductor switching elements with diodes connected in antiparallel, and a charging capacitor, which converts the DC voltage of the charging capacitor into AC and outputs it. In addition, a high-speed mechanical steady short-circuit switch is provided in parallel at the output terminal of each voltage compensation circuit. The charging capacitors in each voltage compensation circuit are charged with different voltages by the charging diode and the charging transformer, and the voltage ratio is set to a power ratio of about 2.

  Constantly, current flows through a steady short circuit switch. Also, when the power system is momentarily reduced, the contact of the steady short circuit switch is opened by the opening command and an arc is generated. Flow in reverse polarity. As a result, a zero current point is forcibly formed in the steady short circuit switch current, and the steady short circuit switch is quickly cut off. After that, the system current flows through the voltage compensation circuit, selects a desired combination from the plurality of voltage compensation circuits according to the error voltage, and compensates the voltage drop of the power system by the sum of the output voltages (for example, patents) Reference 1).

JP 2002-359929 A

In the conventional voltage compensator as described above, the steady short-circuit switch is cut off when a system voltage suddenly drops, the system current is switched to flow through the voltage compensation circuit, and the compensation voltage is superimposed on the system voltage to compensate the voltage. Perform the action.
By the way, when a voltage drop occurs in the system voltage, it is desirable to start the compensation operation as soon as possible, but it is necessary to start the compensation operation after the steady short-circuit switch is opened. And required a predetermined delay time. For this reason, there is a problem in that there is a limit to performing the transition from the occurrence of the instantaneous drop to the compensation operation at high speed.

  The present invention has been made to solve the above-described problems, and is a switching device for switching a switching circuit such as a voltage compensation circuit and a mechanical relay connected in parallel to the switching circuit. An object of the present invention is to speed up a series of switching operations to cut off the current flowing through and switch to power supply via the switching circuit.

  The switching device according to the present invention is a device configuration that includes a mechanical relay connected to a power source and a switching circuit connected in parallel to the mechanical relay to supply power to a load, and between the two poles of the mechanical relay. Is provided with a detection circuit for detecting the opening of the mechanical relay. In addition, the detection circuit includes a current source connected in parallel to the mechanical relay, a voltage limit unit that can be energized when the mechanical relay is connected in parallel and exceeds a predetermined voltage, and a current that flows through the voltage limit unit. Current detecting means for detecting, and inflow preventing means for preventing the current flowing between the power source and the load from flowing into the detecting circuit. When the mechanical relay is opened, the current detection means detects that the current from the current source that was flowing through the mechanical relay flows through the voltage limit means, and detects the opening of the mechanical relay. To do.

  In the switching device according to the present invention, when the mechanical relay is opened, the opening of the mechanical relay can be detected at a high speed, so that the switching operation to the power supply via the switching circuit can be speeded up.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below. FIG. 1 is a schematic configuration diagram of a switching device according to Embodiment 1 of the present invention.
As shown in FIG. 1, power from the AC power source 1 is connected to a load 20 via a voltage compensation circuit 3 as a bidirectional switching circuit, and power is supplied. Further, when the mechanical relay 4 for bypassing the voltage compensation circuit 3 is connected in parallel to the voltage compensation circuit 3 and the power supply voltage is steady, the mechanical relay 4 is closed to bypass the voltage compensation circuit 3 and the power supply voltage decreases. Then, the mechanical relay 4 is opened to switch to the power supply via the voltage compensation circuit 3. The voltage compensation circuit 3 outputs a compensation voltage and superimposes this compensation voltage on the power supply voltage and supplies it to the load 20.

  Further, an open circuit detection circuit 21 that detects a current interruption of the mechanical relay 4, that is, an open circuit, is connected between both poles of the mechanical relay 4. The open circuit detection circuit 21 is connected in parallel with the mechanical relay 4 and becomes capable of energization when exceeding a predetermined voltage (hereinafter referred to as a limit voltage), and a current detector connected in series to the voltage limit means 22. 23 and a current source 24 connected in parallel with the mechanical relay 4. Furthermore, an inflow prevention means 25 for preventing the main line current from the AC power supply 1 to the load 20 from flowing into the open circuit detection circuit 21 is provided. Further, the limit voltage of the voltage limit means 22 is set to a voltage lower than the switching ON voltage in the power supply through the circuit by the voltage compensation circuit 3.

In such a switching device, the operation of the open circuit detection circuit 21 will be described below.
When the mechanical relay 4 is in a closed state and power is being supplied from the AC power supply 1 to the load 20 via the mechanical relay 4, the voltage limit means 22 does not conduct current below the limit voltage, so the current from the current source 24 is It flows on the mechanical relay 4 side.
Next, when the mechanical relay 4 is opened, when the mechanical relay 4 is opened, the voltage between the two poles of the mechanical relay 4 rises. When the voltage between the two poles exceeds the limit voltage, the current of the current source 24 becomes the voltage limit means 22. Flowing. The current detector 23 detects the current flowing through the voltage limit means 22 and detects the opening of the mechanical relay 4.

  When the opening of the mechanical relay 4 is detected, the power supply is quickly switched to power supply via the voltage compensation circuit 3, and the voltage compensation circuit 3 performs a compensation operation for superimposing the compensation voltage on the power supply voltage. Since the limit voltage of the voltage limit means 22 is lower than the switching ON voltage in the voltage compensation circuit 3, the current from the current source 24 continues to flow through the voltage limit means 22 in the open circuit detection circuit 21 even during the compensation operation. . Since the open circuit detection circuit 21 includes the inflow prevention means 25, the main line current from the AC power source 1 to the load 20 does not flow through the voltage limit means 22 even when the voltage limit means 22 is energized. Absent.

Thus, when the mechanical relay 4 is opened, the open circuit of the mechanical relay 4 can be detected by the open circuit detection circuit 21 at high speed. Further, the open circuit detection circuit 21 includes a current source 24 and a voltage limit means 22 and is configured to detect that a current from the current source 21 flows through the voltage limit means 22, so that the power supply voltage is near zero. Even if the load 20 is very low or the load 20 is very small, the open circuit of the mechanical relay 4 can be detected by a stable and reliable operation regardless of the polarity of the power supply voltage, the drop level, and the magnitude of the load. .
By the way, in the voltage compensation circuit 3, it is desirable to start the compensation operation as soon as possible when the power supply voltage drops, but it is necessary to start the compensation operation after the mechanical relay 4 is opened. In this embodiment, since the open circuit detection circuit 21 is provided and the open circuit of the mechanical relay 4 is detected at high speed, a highly reliable switching operation to the compensation operation can be performed at high speed.

Embodiment 2. FIG.
Next, an example of a specific configuration of the open circuit detection circuit 21 in the switching device according to the first embodiment will be described in detail with reference to FIG.
As shown in the figure, the first open circuit detection circuit 21a for detecting the open circuit of the mechanical relay 4 when the power supply voltage of the AC power supply 1 is positive, and the open circuit of the mechanical relay 4 is detected when the power supply voltage is negative. And the second open circuit detection circuit 21b for the purpose, the open circuit detection circuit 21 shown in the first embodiment is used. The first open circuit detection circuit 21a is connected in parallel with the mechanical relay 4 and is connected to a first photocoupler 22a as a first voltage limit means that can be energized when a predetermined voltage (hereinafter referred to as a limit voltage) is exceeded. A first capacitor 24a1 and a first impedance 24a2 as a first current source 24a (24a1, 24a2) connected in parallel with the relay 4, an inflow prevention diode 25a as an inflow prevention means, and a first capacitor 24a1 And an impedance 26a for charging. The second open circuit detection circuit 21b is connected in parallel with the mechanical relay 4 and is supplied with a second photocoupler 22b as second voltage limit means that can be energized when a predetermined voltage (hereinafter referred to as a limit voltage) is exceeded. The second capacitor 24b1 and the second impedance 24b2 as the second current source 24b (24b1, 24b2) connected in parallel with the mechanical relay 4, the inflow prevention diode 25b as the inflow prevention means, and the second capacitor And an impedance 26b for charging 24b1.

Each of the first photocoupler 22a and the second photocoupler 22b includes a plurality of diodes and a current sensor, and each has a limit voltage of 1.5 V, for example, lower than the switching ON voltage in the voltage compensation circuit 3. And when the voltage exceeds the limit voltage, the current is detected and the current sensor detects the current. Each inflow prevention diode 25a (25b) is connected to a diode constituting the first photocoupler 22a (second photocoupler 22b) in the opposite polarity to prevent inflow together with the first photocoupler 22a (second photocoupler 22b). It functions as a means and prevents the main line bidirectional current from flowing from the AC power source 1 to the load 20.
A zener diode is connected in parallel to each capacitor 24a1 (24b1), and a current is supplied to the open circuit detection circuit 21a (21b) by a current source 24a (24b) composed of the capacitor 24a1 (24b1) and an impedance 24a2 (24b2). Supplied.

The operation of the first and second open circuit detection circuits 21a and 21b configured as described above will be described below with reference to FIGS. In the figure, reference numerals 31 to 33 denote a plurality of voltage compensation units constituting the voltage compensation circuit 3, and details of the voltage compensation circuit 3 will be described later.
When the mechanical relay 4 is in a closed state and power is supplied from the AC power supply 1 to the load 20 via the mechanical relay 4, the first photocoupler 22a and the second photocoupler 22b are not energized below the limit voltage, respectively. In the first open circuit detection circuit 21a, as shown in FIG. 3A, the current from the first current source 24a (24a1, 24a2) flows through the mechanical relay 4 side. Similarly, in the second open circuit detection circuit 21b, as shown in FIG. 3B, the current from the second current source 24b (24b1, 24b2) flows on the mechanical relay 4 side.

Next, when the mechanical relay 4 is opened, the voltage between the two poles of the mechanical relay 4 increases when the mechanical relay 4 is opened. As shown in FIG. 4A, when the power supply voltage of the AC power supply 1 is positive, the first photocoupler is reached when the voltage between both electrodes of the mechanical relay 4 exceeds the limit voltage of the first photocoupler 22a. 22a is energized, and the current of the first current source 24a flows through the first photocoupler 22a, and the energization current is detected by a current sensor. Thereby, the opening of the mechanical relay 4 is detected.
Further, as shown in FIG. 4B, when the power supply voltage of the AC power supply 1 is negative, the second voltage is exceeded when the voltage between both electrodes of the mechanical relay 4 exceeds the limit voltage of the second photocoupler 22b. The photocoupler 22b is energized, the current of the second current source 24b flows through the second photocoupler 22b, and the energization current is detected by a current sensor. Thereby, the opening of the mechanical relay 4 is detected.

  As described above, the first open circuit detection circuit 21a and the second open circuit detection circuit 21b can detect the open circuit of the mechanical relay 4 at a high speed when the mechanical relay 4 is opened regardless of the polarity of the power supply voltage. An effect equivalent to that of Form 1 is obtained.

Embodiment 3 FIG.
In the switching device shown in the second embodiment, if the load 20 is a reactor load, the direct current is almost 0Ω, so that the mechanical relay 4 is opened when the AC power source 1 is short-circuited or during a power failure. Even in this case, the voltage between the two poles of the mechanical relay 4 may not exceed the limit voltage of the photocoupler 22a (22b), and it may be impossible to detect an open circuit.
In this embodiment, the first impedance 24a2 in the first open circuit detection circuit 21a is changed at a predetermined cycle of, for example, 10 to 20 kHz, and the current from the first current source 24a is increased in frequency. Thereby, even if the load 20 is a reactor load, the impedance of the load 20 can be made high. Therefore, even when the AC power supply 1 is short-circuited or during a power failure, when the mechanical relay 4 is opened, the voltage between the two poles of the mechanical relay 4 exceeds the limit voltage of the photocoupler 22a, and the photocoupler 22a is energized. Can be detected.

  In addition, since this Embodiment 3 is the structure which assumed the case where the alternating current power supply 1 will be in a short circuit state, and the time of a power failure, the open circuit detection circuit 21a (21b) can be used irrespective of the polarity of a power supply voltage. For this reason, at least one of the first impedance 24a2 in the first open circuit detection circuit 21a or the second impedance 24b2 in the second open circuit detection circuit 21b may be changed in a predetermined cycle.

In the second and third embodiments, the output current value from the first current source 24a in the first open circuit detection circuit 21a and the second current source 24b in the second open circuit detection circuit 21b. The difference from the output current value is set to a predetermined value or more.
If both output current values are equal, even if the mechanical relay 4 is opened, current flows as follows. That is, the electric charge charged in the first capacitor 24a1 flows through a closed loop that returns to the first capacitor 24a1 via the second capacitor 24b1, and the photocoupler 22a (22b) is not energized. For this reason, for example, the output current value from the first current source 24a in the first open circuit detection circuit 21a is set to 170 mA, and the output current value from the second current source 24b in the second open circuit detection circuit 21b is set to 20 mA. If the difference is equal to or greater than a predetermined value, the opening of the mechanical relay 4 can be detected reliably.

Embodiment 4 FIG.
Next, the voltage compensation circuit 3 used in the bidirectional switching circuit in the first to third embodiments will be described in detail with reference to FIG. In this case, the voltage compensation circuit 3 is connected to the power system as the AC power supply 1 and operates so as to compensate for an instantaneous drop in the system voltage.
As shown in the figure, the power supplied from the power system via the transmission line 1 a is stepped down by the transformer 2 and supplied to the consumer (load 20) via the voltage compensation circuit 3. The voltage compensation circuit 3 includes a plurality of (in this case, three) voltage compensation units 31 to 33 connected in series with the power system, and a mechanical relay 4 connected in parallel to bypass the voltage compensation circuit 3. And a control circuit 5 that performs power feeding control.

Each of the voltage compensation units 31 to 33 outputs a compensation voltage with either positive or negative polarity, and compensates for an instantaneous drop in the system voltage by superimposing it on the system voltage. Each voltage compensation unit 31 to 33 includes first to third bit inverters a1 to a3 as a full-bridge single-phase inverter composed of four IGBTs 8 to 11 having diodes connected in antiparallel, and energy storage means. Capacitors 7a1 to 7a3, charging diodes 17a1 to 17a3 and resistors 6a1 to 6a3 constituting a half-wave rectifier circuit for charging each capacitor 7a1 to 7a3, and secondary windings 13a1 to 13a3 of the charging transformer 14 Provided. The AC sides of the first to third bit inverters a1 to a3 are connected in series to the power system. A common primary winding 12 is connected to the power system on the primary side of the charging transformer.
Further, the first to third bit inverters a1 to a3 may be formed of self-extinguishing semiconductor switching elements other than the IGBTs 8 to 11.

Charging voltages V1 to V3 of capacitors 7a1 to 7a3 are connected to the power system with either positive or negative polarity by on / off control of IGBTs 8 to 11. The ratio of the voltages charged in the capacitors 7a1 to 7a3 in each voltage compensation unit 31 to 33 is set to a power ratio of 2. That is, the following relationship is satisfied.
V3 = 2 × V2 = 2 × 2 × V1
The capacitance ratio of the capacitors 7a1 to 7a3 is 4: 2: 1, and the ratio of the resistors 6a1 to 6a3 is 1: 2: 4.

The mechanical relay 4 and the four IGBTs 8 to 11 in each of the bit inverters a1 to a3 are connected to a control circuit 5 that monitors the system voltage, detects the instantaneous drop, and performs power supply control based on the voltage drop.
When the control circuit 5 detects an instantaneous drop in the system voltage, the control circuit 5 generates a contact opening command 4a for the mechanical relay 4 and selects a combination of voltage compensation units 31 to 33 for generating a compensation voltage. Drive signals 8a1 to 11a1, 8a2 to 11a2, and 8a3 to 11a3 of 33 bit inverters a1 to a3 are generated. The voltage compensation circuit 3 can generate a compensation voltage of 0 to 7 gradations based on the sum of output voltages generated from the voltage compensation units 31 to 33, and the maximum compensation voltage is Vc = 7 × V1. It becomes.

When the system voltage is steady, the mechanical relay 4 is in a closed state, and current flows through the mechanical relay 4. When the system voltage is instantaneously reduced, the mechanical relay 4 is opened, and the voltage compensation circuit 3 generates a compensation voltage and superimposes it on the system voltage so that the reference voltage is the target voltage as shown in FIG. . At this time, each of the bit inverters a1 to a3 outputs a voltage as shown in FIG. 6B, and these outputs are combined in the system to perform voltage compensation with a compensation voltage of 8 gradations with high accuracy.
The capacitors 7a1 to 7a3 are slowly charged using a charging transformer 14 whose primary side is connected to the system.

  In this way, in the switching device using the voltage compensation circuit 3 that accurately compensates the voltage with the compensation voltage by the multi-gradation control, the opening circuit of the mechanical relay 4 is opened at high speed by including the opening detection circuit 21 according to the second and third embodiments. Thus, the reliability of the voltage compensation operation including the switching operation is further increased.

Embodiment 5. FIG.
In the switching device shown in each of the above embodiments, the current interruption when the mechanical relay 4 is opened will be described below with reference to FIG.
The voltage compensation circuit 3 includes a plurality of semiconductor switching elements such as IGBTs having diodes connected in antiparallel, and constitutes a bidirectional switching circuit. However, the on-voltage at the time of power supply via the voltage compensation circuit 3 is mechanically It is assumed that the voltage is lower than the arc voltage generated when the relay 4 is opened. In addition, although the arc voltage of the mechanical relay 4 interrupted in the air is, for example, 30 V, the on-voltage of one IGBT is, for example, 2 V, the on-voltage of the voltage compensation circuit 3 including a plurality of IGBTs is It can be configured to be lower than the arc voltage.
Then, when the mechanical relay 4 is opened, the switching state of the voltage compensation circuit 3 is short-circuited between both terminals on the power supply side and the load side in advance.

Even if the switching state of the voltage compensation circuit 3 is short-circuited between both terminals on the power supply side and the load side before the mechanical relay 4 is opened, the mechanical relay 4 is in a closed state and the mechanical relay 4 having almost no loss is provided. Power is supplied from the AC power supply 1 to the load 20 via Next, when the mechanical relay 4 is opened, the contact of the mechanical relay 4 is released and an arc voltage is generated. However, since the ON voltage in the switching state in which the power supply side and load side terminals of the voltage compensation circuit 3 are short-circuited is lower than the arc voltage, the voltage between the two poles of the mechanical relay 4 rises and the arc voltage Is commutated to the voltage compensation circuit 3 side sooner than the time when the mechanical relay 4 is cut off at high speed.
Thereafter, the switching state of the voltage compensation circuit 3 is switched, and a compensation operation for outputting the compensation voltage and superimposing it on the power supply voltage is performed.

  As described above, in the voltage compensation circuit 3, it is desirable to start the compensation operation as soon as possible when a power supply voltage drop occurs, but it is necessary to start the compensation operation after the mechanical relay 4 is opened. In this embodiment, the mechanical relay 4 can be disconnected at a high speed faster than the arc voltage is generated, and the switching operation to the compensation operation can be performed at a high speed.

Further, when the open circuit detection circuit 21 shown in the first to third embodiments is also provided, the mechanical relay 4 can be cut off at a higher speed than the generation of the arc voltage, and the open circuit (cutoff) is opened. Since detection can be performed at high speed by the detection circuit 21, a highly reliable switching operation to the compensation operation can be performed at higher speed.
Note that the limit voltage at which the voltage limit means 22 used in the open circuit detection circuit 21 can be energized is lower than the ON voltage in the switching state in which both the power supply side and load side terminals of the voltage compensation circuit 3 are short-circuited. The open circuit detection circuit 21 detects the open circuit earlier than the commutation to the circuit 3 side and the mechanical relay 4 interrupts, but there is no problem because the open circuit is detected immediately after the open circuit is detected.

  In the above embodiments, the voltage compensation circuit 3 is connected to the AC power supply 1. However, the present invention is not limited to the voltage compensation circuit 3, and other bidirectional switching circuits using semiconductor switching elements may be used. A similar effect can be obtained.

  Further, as shown in FIG. 8, a DC power supply 41 may be used instead of the AC power supply 1, and in that case, a unidirectional switching circuit 42 including a semiconductor switching element can be applied as a switching circuit. In the case of such power supply from the DC power supply 41, the arc voltage that has conventionally been generated when the mechanical relay 4 is opened does not have a zero cross point, so that it takes about 30 ms to cut off, for example. . Here, the ON voltage of the unidirectional switching circuit 42 is assumed to be lower than the arc voltage generated when the mechanical relay 4 is opened, and when the mechanical relay 4 is opened, the switching state of the unidirectional switching circuit 42 is changed in advance to the power supply side, A short circuit is established between both terminals on the load side. For this reason, when the mechanical relay 4 is opened, commutation to the unidirectional switching circuit 42 side occurs earlier than the generation of the arc voltage, and the mechanical relay 4 is cut off at high speed, for example, in a time of about 5 ms.

Embodiment 6 FIG.
Next, in the fifth embodiment, the detection of the opening of the mechanical relay 4 using another method will be described with reference to FIG.
As shown in the figure, power from the AC power source 1 is connected to a load 20 via a voltage compensation circuit 3 serving as a bidirectional switching circuit, and power is supplied. Further, when the mechanical relay 4 for bypassing the voltage compensation circuit 3 is connected in parallel to the voltage compensation circuit 3 and the power supply voltage is steady, the mechanical relay 4 is closed to bypass the voltage compensation circuit 3 and the power supply voltage decreases. Then, the mechanical relay 4 is opened to switch to the power supply via the voltage compensation circuit 3. The voltage compensation circuit 3 outputs a compensation voltage and superimposes this compensation voltage on the power supply voltage and supplies it to the load 20.
In addition, a current detector 43 that detects an energization current of the mechanical relay 4 is connected to the mechanical relay 4 in series.

  Further, as shown in the fifth embodiment, the voltage compensation circuit 3 includes a plurality of semiconductor switching elements such as IGBTs having diodes connected in antiparallel, and constitutes a bidirectional switching circuit. It is assumed that the ON voltage for supplying power via the compensation circuit 3 is lower than the arc voltage generated when the mechanical relay 4 is opened. Then, when the mechanical relay 4 is opened, the switching state of the voltage compensation circuit 3 is short-circuited between both terminals on the power supply side and the load side in advance.

In this embodiment, when the mechanical relay 4 is opened, the current detector 43 detects the energization current of the mechanical relay 4 to quickly detect the opening of the mechanical relay 4.
For this reason, since the mechanical relay 4 can be shut off at a high speed faster than the arc voltage is generated, and the open circuit (breaking) can be detected promptly, a reliable switching operation to the compensation operation is performed at a high speed. be able to.
Further, such open circuit detection can be applied when the load 20 is more than a certain level, and quick open circuit detection is possible regardless of the level of decrease in the power supply voltage.

Instead of providing the current detector 43 for detecting the open circuit, a voltage detector 44 for detecting the voltage across the mechanical relay 4 may be provided as shown in FIG. When the mechanical relay 4 is opened when the mechanical relay 4 is opened, the voltage between both poles of the mechanical relay 4 increases. By detecting this increased voltage with the voltage detector 44, the opening of the mechanical relay 4 can be detected quickly. Therefore, a highly reliable switching operation to the compensation operation can be performed at high speed.
Further, such open circuit detection by the voltage detector 44 can be applied in a state where the power supply voltage is not near zero, and rapid open circuit detection is possible regardless of the size of the load 20.

Embodiment 7 FIG.
Although the voltage compensation circuit 3 used in the bidirectional switching circuit of the switching device according to each of the above embodiments has been described in the fourth embodiment, another example of the voltage compensation circuit 3 will be described below.
FIG. 11 is a diagram showing a configuration of a switching device according to Embodiment 7 of the present invention. Since the voltage compensation circuit 3 is mainly shown, the illustration of the AC power supply 1 and the load 20 is omitted for convenience.
As shown in the figure, the voltage compensation circuit 3 is composed of a plurality (in this case, four) of voltage compensation units 31 to 34 connected in series to the AC power supply 1, and is connected in parallel to bypass the voltage compensation circuit 3. The mechanical relay 4 connected to is provided.

Each voltage compensation unit 31 to 34 outputs a compensation voltage with either positive or negative polarity, and compensates for a decrease in the power supply voltage by superimposing it on the power supply voltage. Each voltage compensation unit 31 to 34 includes four IGBTs having diodes connected in antiparallel, or first to fourth bit inverters a1 to a4 as a full-bridge single-phase inverter composed of MOSFETs, and a Zener diode D1. ˜D4 includes capacitors C1 to C4 as energy storage means connected in parallel.
The charging voltages V1 to V4 of the capacitors C1 to C4 are connected to the power system with either positive or negative polarity by on / off control of the IGBT and MOSFET. The ratio of the voltages charged in the capacitors C1 to C4 in each voltage compensation unit 31 to 34 is set to a power ratio of 2, that is, 1: 2: 4: 8.

  When the power supply voltage is steady, the mechanical relay 4 is in a closed state, and current flows through the mechanical relay 4. When the power supply voltage drops momentarily, the mechanical relay 4 is opened, and the voltage compensation circuit 3 generates a compensation voltage so as to be the reference voltage and superimposes it on the power supply voltage. At this time, the outputs of the bit inverters a1 to a4 are combined to perform voltage compensation with high accuracy using a compensation voltage of 16 gradations.

As shown in the figure, the first and second charging circuits 50 and 51 are connected between the terminals of the capacitors C3 and C4 in the voltage compensation units 33 and 34, in this case, on the negative electrode side, between the power supply terminals. . Reference numerals 56 and 63 are resistors.
The first charging circuit 50 connected to the capacitor C3 includes a transistor 52, a Zener diode 53, a resistor 54, and a diode 55, and allows a constant charging current to flow while keeping the voltage applied to the resistor 54 constant. In this case, the AC power supply 1 is connected to the first to third bit inverters a1 to a3 by the charging current flowing through the mechanical relay 4, the first to third bit inverters a1 to a3, and the first charging circuit 50. The capacitors C1 to C3 are charged. The second charging circuit 51 connected to the capacitor C4 includes a transistor 57, a Zener diode 58, a resistor 59 and a diode 60, a switching element 61 and a resistor 62, and makes the voltage applied to the resistor 59 constant. A constant charging current is passed. In this case, the capacitor C4 is charged by the charging current flowing from the AC power supply 1 via the fourth bit inverter a4 and the second charging circuit 51.

  The charging of the capacitors C1 to C4 is performed in a state where power is supplied to the load via the mechanical relay 4 at the normal time, and is not performed during the compensation operation. Further, the capacitors C1 to C4 can be charged via the bit inverters a1 to a4 by turning off all the four switching elements A to D in the first to fourth bit inverters a1 to a4.

In this embodiment, the charging circuits 50 and 51 are provided, and the capacitors C1 to C4 are charged from the AC power source 1 through the bit inverters a1 to a4. Therefore, a charging transformer is not required, and the apparatus is small and simple. Can be charged with configuration.
Further, only the capacitor C4 connected to the fourth bit inverter a4 that requires a high voltage is charged using the second charging circuit 51, and the capacitors C1 to C3 connected to the other three bit inverters a1 to a3, respectively. Since C3 is charged using the common first charging circuit 50, the circuit configuration for charging is further simplified and efficient charging is possible.

The three capacitors C1 to C3 that are charged using the first charging circuit 50 can be charged by selecting a desired combination of the capacitors C1 to C3. When charging all of the capacitors C1 to C3, charging is performed through the charging current path shown in FIG. 12. For example, when charging only the capacitors C1 and C3, charging is performed through the charging path illustrated in FIG. At this time, by turning on only the switching element D of the second bit inverter a2 and turning off all the other switching elements, the power source side and load side terminals of the second bit inverter a2 are short-circuited, and the capacitor C2 Deviates from the charging path, and only the capacitors C1 and C3 can be charged. As described above, the circuit configuration is simple using the common first charging circuit 50, and the desired combination of capacitors C1 to C3 can be selected and charged by switching control of the bit inverters a1 to a3. The battery can be charged more efficiently with good control of the charging voltage.
FIG. 12 and FIG. 13 are explanatory diagrams showing how the capacitors C1 to C3 connected to the three bit inverters a1 to a3 are charged using the first charging circuit 50, and other circuit configurations are as follows. For convenience, the illustration is omitted.

It is a schematic block diagram of the switching apparatus by Embodiment 1 of this invention. It is a circuit block diagram of the switching apparatus by Embodiment 2 of this invention. It is a circuit diagram explaining the operation | movement of the switching apparatus by Embodiment 2 of this invention. It is a circuit diagram explaining the operation | movement of the switching apparatus by Embodiment 2 of this invention. It is a circuit block diagram of the voltage compensation circuit by Embodiment 4 of this invention. It is a figure explaining operation | movement of the voltage compensation circuit by Embodiment 4 of this invention. It is a circuit block diagram of the switching apparatus by Embodiment 5 of this invention. It is a circuit block diagram of the switching apparatus by another example of Embodiment 5 of this invention. It is a circuit block diagram of the switching apparatus by Embodiment 6 of this invention. It is a circuit block diagram of the switching apparatus by another example of Embodiment 6 of this invention. It is a circuit block diagram of the voltage compensation circuit by Embodiment 7 of this invention. It is a circuit diagram explaining the charging operation of the voltage compensation circuit by Embodiment 7 of this invention. It is a circuit diagram explaining the charging operation of the voltage compensation circuit by Embodiment 7 of this invention.

Explanation of symbols

1 AC power supply, 2 voltage compensation circuit, 4 mechanical relay,
7a1-7a3 capacitor, 20 load, 21 open circuit detection circuit,
21a first open circuit detection circuit, 21b second open circuit detection circuit, 22 voltage limit means, 22a first photocoupler as first voltage limit means,
22b Second photocoupler as second voltage limit means, 23 Current detector,
24 current source, 24a1 first capacitor, 24a2 first impedance,
24b1 second capacitor, 24b2 second impedance, 25 inflow prevention means,
25a, 25b inflow prevention diode, 31-34 voltage compensation unit,
41 DC power supply, 42 unidirectional switching circuit, 43 current detector,
44 voltage detector, 50 first charging circuit, 51 second charging circuit,
a1 1st bit inverter as a single phase inverter,
a2 Second bit inverter as a single phase inverter,
a3 Third bit inverter as a single phase inverter,
a4 Fourth bit inverter as a single-phase inverter, C1 to C4 capacitors.

Claims (11)

In a switching device for supplying power to a load comprising a mechanical relay connected to a power source and a switching circuit connected in parallel to the mechanical relay,
A detection circuit for detecting an open circuit of the mechanical relay is provided between both poles of the mechanical relay,
The detection circuit detects a current source in which the mechanical relay is connected in parallel, a voltage limit unit that is energized when the mechanical relay is connected in parallel and exceeds a predetermined voltage, and a current that is supplied to the voltage limit unit. Current detection means, and inflow prevention means for preventing the current flowing between the power source and the load from flowing into the detection circuit,
When the mechanical relay is opened, the current detection means detects that the current from the current source that was flowing through the mechanical relay flows through the voltage limit means, and detects the opening of the mechanical relay. A switching device characterized by the above. 2. The switching device according to claim 1, wherein a predetermined voltage at which the voltage limiting means in the detection circuit can be energized is lower than an on-voltage of the switching circuit. The power supply is an AC power supply, the switching circuit is a bidirectional switching circuit comprising a semiconductor switching element, and the detection circuit is a first detection circuit for detecting an open circuit of the mechanical relay when the power supply voltage is positive. And a second detection circuit for detecting an open circuit of the mechanical relay when the power supply voltage is negative. The current source is composed of a capacitor and an impedance, the voltage limit means is composed of a first diode, and the inflow preventing means is connected to the first diode and the second diode connected to each other in the opposite polarity. 4. The switching device according to claim 3, wherein the switching device is constituted by a diode. 5. The switching device according to claim 4, wherein the impedance of the current source of the detection circuit is changed at a predetermined period. 6. The difference between the output current value from the current source of the first detection circuit and the output current value from the current source of the second detection circuit is set to a predetermined value or more. Switching device. The switching circuit is a voltage compensation circuit that has energy storage means, converts a DC voltage stored in the energy storage means into alternating current, and outputs a compensation voltage superimposed on the voltage from the power supply to the load. Yes, when the power supply voltage is steady, the mechanical relay is closed to bypass the voltage compensation circuit, and when the power supply voltage is lowered, the mechanical relay is opened, and after the detection circuit detects the opening of the mechanical relay, 7. The switching device according to claim 1, wherein the compensation voltage is supplied to the load by superimposing the compensation voltage on the power supply voltage by the voltage compensation circuit. 3. The switching device according to claim 1, wherein the power source is a DC power source, and the switching circuit is a unidirectional switching circuit composed of a semiconductor switching element. The on-voltage of the switching circuit for short-circuiting both terminals on the power supply side and the load side of the switching circuit is configured to be lower than the arc voltage generated when the mechanical relay is opened, and when the mechanical relay is opened The switching device according to any one of claims 1 to 8, wherein the switching state of the switching circuit is previously short-circuited between the two terminals. The voltage compensation circuit comprises a capacitor as the energy storage means, and is configured by connecting the AC side of a plurality of single-phase inverters that convert and output the charging voltage of the capacitor to AC in series with the power source, A desired combination is selected from the plurality of single-phase inverters, and the compensation voltage is generated by the sum of output voltages. The capacitors are connected to the single-phase inverter from the power source when the power source voltage is steady. The switching device according to claim 7 , wherein the switching device is charged via a switch. By providing a common charging circuit that charges each capacitor with current flowing through the plurality of single-phase inverters connected in series, and short-circuiting the desired single-phase inverter between both terminals on the power supply side and the load side The switching device according to claim 10 , wherein a capacitor connected to the single-phase inverter is removed from the charging path.

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