JP3818302B2 - Uninterruptible power system - Google Patents

Description

  The present invention relates to an uninterruptible power supply that suppresses a decrease in load voltage when a voltage drop accident such as an instantaneous voltage drop or a power failure occurs in a commercial power supply.

  In a computer system equipped with a device such as a semiconductor manufacturing device or a network server, a power failure such as a power failure or instantaneous voltage drop (hereinafter referred to as “instantaneous drop”) may cause serious damage. Therefore, recently, an uninterruptible power supply is often used as a standby power supply in the above devices and systems. A general uninterruptible power supply is equipped with a battery (storage battery). When the power is normal (normal), the battery is charged, and when a power failure occurs, the battery or device is supplied with power. Thus, it is possible to prevent the device or the system from being stopped or malfunctioning, and to function normally, or to safely shut down the system.

Some uninterruptible power supplies use a flywheel as a power storage means instead of a battery (see, for example, Patent Document 1).
JP 2001-178023 A

  In the conventional uninterruptible power supply, if a power supply accident such as a voltage sag or a power failure occurs in the commercial power supply, the uninterruptible power supply detects the voltage drop in the internal control circuit and quickly turns off the high-speed circuit breaker. Disconnect and start the converter to supply power to the load.

  However, in the conventional uninterruptible power supply, there is no compensation voltage during the delay time (within several msec) until the voltage drop is detected in the control circuit, and the load voltage is several msec until the high-speed circuit breaker is turned off. In the worst case, the load voltage may be reduced by 100%. In addition, in the case of the network server or the semiconductor manufacturing apparatus, there is a possibility that the apparatus or the system may be stopped or the product being manufactured may be damaged even if the load voltage decreases by about 50%. there were.

  Therefore, for devices that are sensitive to power supply accidents such as network servers and semiconductor manufacturing devices, conventionally, only an inverter-less uninterruptible power supply with an operating efficiency of about 90% and not very efficient can be used as a standby power supply. There was a problem.

  Then, an object of this invention is to provide the uninterruptible power supply device which can suppress the fall of load voltage before the accident occurs in a commercial power source and a high-speed circuit breaker turns off.

  The present invention has the following configuration as means for solving the above problems.

(1) Accident detection means for detecting an abnormality in which the voltage of the commercial power supply decreases;
A distribution transformer that transforms a high voltage distributed from the commercial power source into a low voltage that is distributed to a load;
A current-limiting reactor that limits current when an abnormality occurs in the commercial power source, and the commercial power source and the load are connected via the current-limiting reactor when the commercial power source is normal. A high-speed switching means for cutting off the connection between the commercial power supply and the load when an abnormality is detected in the power supply; and a current flowing through the current-limiting reactor when an abnormality occurs in the commercial power supply and after the high-speed switching means is cut off. Recirculation means for recirculation, and high-speed current limiting interrupting means connected to the low voltage side of the distribution transformer,
An interconnection transformer connected in parallel with the load between the high-speed current limiting interrupting means and the load;
Power storage means for storing electric power to be supplied to the load when the commercial power supply is abnormal;
Power conversion means connected between the interconnection transformer and the power storage means, and immediately after the occurrence of an abnormality in the commercial power supply, converts the stored power of the power storage means into AC power and distributes the power to the interconnection transformer; With
The ratio of the sum of the leakage impedance of the distribution transformer and the leakage impedance of the interconnection transformer and the leakage impedance of the interconnection transformer is set to be equal to or less than an allowable reduction rate of the load voltage. And

  In this configuration, the uninterruptible power supply has a current limiting reactor, and the ratio of the sum of the leakage impedance of the distribution transformer and the leakage impedance of the interconnection transformer and the leakage impedance of the interconnection transformer is The load voltage is set to be equal to or less than an allowable decrease rate. Therefore, immediately after an abnormality occurs in the commercial power supply, a voltage is generated in the current-limiting reactor to suppress an increase in current and an effect of suppressing a decrease in load voltage. The drop in the load voltage can be suppressed by the impedance of the flow reactor. In addition, when the current on the AC side passes the peak and current recirculation occurs in the current limiting reactor and the recirculation means, and a period in which the current limiting reactor voltage is zero occurs, the impedance of the current limiting reactor is apparently zero. However, the decrease in load voltage can be suppressed by the leakage impedance of the distribution transformer, the sum of the leakage impedance of the distribution transformer and the leakage impedance of the interconnection transformer, and the leakage impedance of the interconnection transformer Is set to be equal to or less than the allowable decrease rate of the load voltage, and thus it is possible to suppress the load voltage from decreasing beyond the allowable decrease rate.

  For example, when the allowable drop rate of the load voltage is 40%, the capacity of the distribution transformer and the interconnection transformer are the same, and the value of the leakage impedance is 2: 1, the voltage of the bidirectional converter 17 is From the relationship, even when a period in which the current-limiting reactor voltage becomes zero occurs, the load voltage decrease rate can be maintained at about 33%, which is a value equal to or less than the allowable decrease rate. Moreover, since the voltage of the current-limiting reactor voltage can be increased until the current-limiting reactor voltage becomes zero, it is possible to further suppress a decrease in load voltage at the time of an accident.

  In addition, the uninterruptible power supply has a configuration that includes a distribution transformer in advance, so even if the installation environment (system conditions) of the uninterruptible power supply is not investigated in advance, the load will reduce the load voltage by what percentage. It is possible to design based on the allowable reduction rate of the load voltage, which is a specification of whether or not it is acceptable. In addition, almost no adjustment is required when the uninterruptible power supply is installed on site. Furthermore, it is not necessary for the user of the uninterruptible power supply to prepare a distribution transformer according to the load. Therefore, the versatility of the uninterruptible power supply is increased and can be standardized.

  (2) The power conversion means supplies reactive power that cancels reactive power of the load when the commercial power supply is normal.

  In general, if the leakage impedance of the distribution transformer is large, the voltage drop also increases, which may cause problems during normal times. In this configuration, since the reactive power for canceling the reactive power of the load is supplied from the power conversion means, the reactive power of the distribution transformer becomes almost zero, and voltage drop due to leakage impedance can be prevented. As a result, it is possible to compensate for the voltage drop of the distribution transformer caused by increasing the value of the leakage impedance, and to improve the power reception rate.

  (3) The high-speed current limiting interrupting means includes a pair of thyristors as the high-speed switching means and a pair of diodes as the reflux means between two DC terminals of a single-phase rectifier bridge circuit. It is the structure which connected the reactor.

  In this configuration, when an abnormality in the commercial power supply is detected, the thyristor can be extinguished when the load current becomes zero by turning off the ignition signal output to the pair of thyristors. The connection between the commercial power source and the load can be cut off in a short time.

  (4) In the high-speed current limiting interrupting means, the current-limiting reactor and the self-extinguishing switching element that is the high-speed switching means are connected in series between two DC terminals of the single-phase rectifier bridge circuit, A reflux diode as a reflux means is connected in parallel to the current limiting reactor.

  In this configuration, the high-speed current limiting interrupting means includes a self-extinguishing type switching element as a high-speed opening / closing means. Therefore, when a signal for turning off the switching element is output, the commercial power supply and the load are immediately connected. The connection can be cut off. Therefore, the time from detection of an abnormality in the commercial power supply to disconnection of the connection between the generated commercial power supply and the load can be further shortened compared to the configuration of (3). Moreover, since it can interrupt | block more rapidly, since the electric current which flows through structural members, such as a DC reactor and a diode, can be suppressed, the current capacities of each structural member etc. can be set small.

  In addition, by providing the reflux diode in parallel with the DC reactor, the current flowing through the DC reactor can be refluxed, and an overvoltage in the DC reactor can be suppressed.

  (5) The high-speed switching means is characterized in that a current limiting resistor or a capacitor is connected in parallel.

  In this configuration, although the connection between the commercial power supply and the load cannot be completely cut off by the high-speed current limiting cut-off means, the current can be suppressed, so that an uninterruptible power supply device prevents an instantaneous voltage drop with respect to the load. It becomes possible.

  (6) A current-limiting reactor is provided in place of the distribution transformer.

  In this configuration, by providing a current-limiting reactor instead of the distribution transformer, even if the distribution transformer is prepared in advance in the system feeder where the uninterruptible power supply is installed, A decrease in load voltage can be suppressed. In addition, depending on the location of an accident on the commercial power supply side, the leakage impedance of the distribution transformer can be used to prevent the load voltage from being lowered, so that it is possible to further suppress the drop in the load voltage during an abnormality.

  According to the present invention, immediately after an abnormality occurs in the commercial power supply, a voltage is generated in the current limiting reactor to suppress an increase in current and an effect of suppressing a decrease in load voltage. The decrease in the load voltage can be suppressed by the leakage impedance and the impedance of the current-limiting reactor. In addition, when the current on the AC side passes the peak and current recirculation occurs in the current limiting reactor and the recirculation means, and a period in which the current limiting reactor voltage is zero occurs, the impedance of the current limiting reactor is apparently zero. However, the decrease in load voltage can be suppressed by the leakage impedance of the distribution transformer, the sum of the leakage impedance of the distribution transformer and the leakage impedance of the interconnection transformer, and the leakage impedance of the interconnection transformer Is set to be equal to or less than the allowable decrease rate of the load voltage, and thus it is possible to suppress the load voltage from decreasing beyond the allowable decrease rate.

  In addition, the uninterruptible power supply has a configuration that includes a distribution transformer in advance, so even if the installation environment (system conditions) of the uninterruptible power supply is not investigated in advance, the load will reduce the load voltage by what percentage. It is possible to design based on the allowable reduction rate of the load voltage, which is a specification of whether or not it is acceptable. In addition, when an uninterruptible power supply is installed in the field, almost no adjustment is required, and the user of the uninterruptible power supply does not need to prepare a distribution transformer according to the load. Can be high and standardized.

[First Embodiment]
FIG. 1 is a schematic configuration diagram and an equivalent circuit diagram of the uninterruptible power supply according to the first embodiment of the present invention. FIG. 2 is a waveform diagram showing changes in current and voltage of each part before and after the occurrence of an accident on the commercial power supply side.

  The uninterruptible power supply 1 includes an instrument transformer 11, a control unit 12, a distribution transformer 13, a circuit breaker 14, a current limiting circuit 15, a battery 16, a bidirectional converter 17, an interconnection transformer 18, a circuit breaker 19, And a power output measuring unit 20, a commercial power supply 5 is connected to the input terminal 2, and a load 6 is connected to the output terminal 3. Further, the distribution line from the commercial power source 5 to the load 6 is referred to as a system feeder 4.

  The instrument transformer 11 is for measuring the AC voltage distributed from the commercial power supply 5 to detect the occurrence of a power supply accident, and outputs the measurement result to the control unit 12.

  The control unit 12 controls the opening / closing operation of the high-speed opening / closing means of the current limiting circuit 15 and the charging and output operation of the bidirectional converter 17 based on the voltage measurement result of the commercial power supply 5 output from the instrument transformer 11. Further, the control unit 12 controls the output power of the bidirectional converter 17 based on the measurement result of the power output measurement unit 20.

  The distribution transformer 13 transforms the voltage supplied from the commercial power supply 5 into a voltage to be distributed to the load 6.

  The circuit breaker 14 is for cutting off the connection between the commercial power supply 5 and the load 6 during maintenance of the uninterruptible power supply 1. The circuit breaker 14 may have a configuration provided between the input terminal 2 and the distribution transformer 13.

  The current limiting circuit 15 includes two (a pair of) thyristors 21a and 21b, which are high-speed switching means, and two (a pair of) diodes 21c and 21d, and two AC terminals 21a1 and 21a2. Two DC terminals 21d1, 21d2 are provided. The AC terminal 21a1 is connected to the anode of the thyristor 21a and the cathode of the thyristor 21b, and the AC terminal 21a2 is connected to the cathode of the diode 21c and the anode of the diode 21d. The DC terminal 21d1 is connected to the cathode of the thyristor 21a and the cathode of the diode 21d, and the DC terminal 21d2 is connected to the anode of the thyristor 21b and the anode of the diode 21c. Further, a DC reactor 22 is connected between the DC terminal 21d1 and the DC terminal 21d2. In addition, the circuit breaker 14 is connected to the AC terminal 21a1, and the power output measuring unit 20 is connected to the AC terminal 21a2.

  In the current limiting circuit 15, the AC terminal 21 a 1 may be connected to the power output measuring unit 20, and the AC terminal 21 a 2 may be connected to the circuit breaker 14.

  The DC reactor 22 is a current-limiting reactor that limits the current flowing from the bidirectional converter 17 to the commercial power supply 5 when a power failure occurs in the commercial power supply 5.

  The battery 16 stores electric power (electric energy) to be supplied to the load 6 when an abnormality occurs in the commercial power source 5 such as a power failure or instantaneous voltage drop. Note that power storage means such as a flywheel or a capacitor may be used instead of the battery 16.

  The bi-directional converter 17 operates as a charger that charges the battery 16 when the commercial power supply 5 side is normal, and switches to inverter operation when the voltage on the commercial power supply 5 side decreases or an accident occurs on the commercial power supply 5 side. In addition, a continuous operation is performed in which the power of the battery 16 is converted into AC power and supplied to the load 6 without interruption, and operates as a voltage source.

  The interconnection transformer 18 steps down the voltage of the system feeder 4 to a predetermined voltage and distributes it to the bidirectional converter 17. Further, the output voltage of the bidirectional converter 17 is boosted to the same voltage as that of the system feeder 4 and distributed to the system feeder 4.

  The circuit breaker 19 is for disconnecting the primary side of the interconnection transformer 18 connected in parallel to the load 6 from the system feeder 4 at the time of maintenance of the uninterruptible power supply 1.

  The power supply output measuring unit 20 includes AC measuring current transformers 20 a and 20 a 2 and an AC measuring instrument transformer 20 v, measures the inverter current, the load current, and the load voltage, and outputs the results to the control unit 12.

  An equivalent circuit of the uninterruptible power supply 1 shown in FIG. 1A is as shown in FIG. That is, the commercial power supply 5 in which the leakage impedance jXt of the distribution transformer 13 and the inductance Ldc of the DC reactor 22 are connected in series, and the converter power supply (battery 16) in which the leakage impedance jXc of the interconnection transformer 18 is connected in series. And a power source equivalent to the bidirectional converter 17) 17a are connected in parallel to the load 6.

  In FIG. 1B, the power supply voltage of the commercial power supply 5 is VS, the converter voltage of the converter power supply 17a is VC / converter current IC, the load voltage of the load 6 is VL, and the leakage impedance of the distribution transformer 13 is jXt / distribution. The voltage (voltage drop) of the transformer 13 is ΔVt, the inductance of the DC reactor is Ldc, the voltage (voltage drop) of the DC reactor is ΔVdc, the current flowing through the DC reactor is Idc, and the leakage impedance of the interconnection transformer 18 ( (Linkage inductance) is assumed to be jXc.

  As shown in FIG. 2, the power supply current hardly changes at the normal time (before t0). Therefore, the DC reactor current Idc rectified by the thyristors 21a and 21b and the diodes 21c and 21d, which are rectifying elements of the current limiting circuit 15, becomes a substantially constant DC current. That is, the DC reactor voltage ΔVdc≈0.

  On the other hand, the uninterruptible power supply 1 detects a voltage drop by the internal control unit 12 and immediately turns off the thyristors 21a and 21b when an accident such as a momentary voltage drop or a power failure occurs on the commercial power supply 5 side (t0). The operation to disconnect the system is performed. However, since the thyristors 21a and 21b are not turned off (extinguish) unless the load current becomes zero even when the ignition signal is turned off, until the control unit 12 detects a voltage drop and turns off the thyristors 21a and 21b ( A time of several msec is required from t0 to t3). Therefore, the uninterruptible power supply 1 is configured so that the load voltage VL does not fall below a certain value during this delay time (within several msec).

  When an accident such as a momentary voltage drop or a power failure occurs on the commercial power supply 5 side, the power supply voltage VS decreases instantaneously and an excessive current tends to flow from the load 6 side (that is, the converter power supply 17a side) toward the system fault point. (T0 to t1). At this time, since the uninterruptible power supply 1 is provided with the DC reactor 22 as the current limiting circuit 15, the DC reactor current Idc increases via the rectifying element of the current limiting circuit 15, and the voltage Δ is applied to the DC reactor 22. The effect of suppressing the decrease in the load voltage VL can be obtained while Vdc is generated to suppress the increase in current. A voltage obtained by adding the residual voltage ΔVt generated according to the ratio of the leakage impedance between the distribution transformer 13 and the interconnection transformer 18 and the voltage ΔVdc of the current limiting circuit is supplied to the load as the load voltage VL. .

  Subsequently, when the current on the AC side passes the peak, current recirculation occurs in the DC reactor 22 and the diodes 21c and 21d, so that the DC reactor voltage ΔVdc has a period in which ΔVdc≈0 (after t2). Therefore, in the conventional uninterruptible power supply device that does not include the distribution transformer 13, there is no compensation voltage during this period, and in the worst case, the load voltage may be reduced by 100%.

  Therefore, the uninterruptible power supply 1 is provided with a distribution transformer 13 on the primary side of the current limiting circuit 15 as a countermeasure, and the leakage impedance jXt of the distribution transformer 13 is controlled to suppress a decrease in the load voltage VL. For use.

  That is, since the residual voltage is lowered only by the current limiting circuit 15, the leakage impedance of the distribution transformer 13 and the interconnection transformer 18 with respect to the distribution transformer 13 incorporated in the system of the uninterruptible power supply 1. Is adjusted to obtain the base voltage of the residual voltage. For example, if the distribution transformer 13 and the interconnection transformer 18 have the same capacity and the same leakage impedance value, a period of ΔVdc≈0 may occur due to the voltage of the bidirectional converter 17. The base residual voltage of the load voltage VL can be maintained at about 50% at the minimum. Further, since the voltage ΔVdc of the DC reactor 22 can be added until ΔVdc≈0, it is possible to further suppress the decrease in the load voltage VL at the time of an accident. This relationship is expressed as follows.

In the uninterruptible power supply 1, the bidirectional converter operates in an interconnected manner. For example, when considering the case where VS = 0 as the worst condition, the load voltage VL is
VL = VC-jXc · IC
≒-(△ Vt + △ Vdc)
= − (JXt · IS) −Ldc {d (Idc) / dt}
It becomes.

  The residual rate of the load voltage VL varies depending on the impedance of the distribution transformer 13 and the DC transient impedance of the DC reactor 22 provided in the current limiting circuit 15, but the leakage impedance of the distribution transformer 13 and the interconnection transformer By setting the ratio of the sum of the leakage impedance of 18 and the leakage impedance of the interconnecting transformer 18 to be equal to or less than the allowable reduction rate of the load voltage, when the accident occurs, the ratio between the commercial power source 5 and the load 6 is reduced. It is possible to reliably prevent the load voltage from reaching a value exceeding the allowable decrease rate before the interruption.

  For example, when the allowable drop rate of the load voltage is 40%, the capacity of the distribution transformer and the interconnection transformer are the same, and the value of the leakage impedance is 2: 1, the voltage of the bidirectional converter 17 is From the relationship, even when a period in which the current-limiting reactor voltage becomes zero occurs, the load voltage decrease rate can be maintained at about 33%, which is a value equal to or less than the allowable decrease rate. Moreover, since the voltage of the current-limiting reactor voltage can be increased until the current-limiting reactor voltage becomes zero, it is possible to further suppress a decrease in load voltage at the time of an accident.

  Therefore, when a fault occurs on the system side, based on the converter voltage VC, the residual voltage generated according to the ratio of the leakage impedances of both transformers, or the residual voltage and the voltage ΔVdc of the current limiting circuit are added together. The voltage can be supplied to the load as a load voltage VL.

Further, in normal times, the load voltage VL has a relationship represented by the following expression. That is,
VL = VC-jXc · IC
≒-(△ Vt + △ Vdc)
= − (JXt · IS) −Ldc {d (Idc) / dt}
= -JXt · IS
∵d (Idc) / dt≈0 in steady state
Thus, a voltage drop occurs in proportion to the value of the leakage impedance of the distribution transformer.

  Therefore, by setting the leakage impedance of the distribution transformer 13 to a large value, reactive power (usually phase-advanced reactive power) is output from the bidirectional converter 17 when the influence of a voltage drop during normal operation is large. Thus, the voltage drop due to the leakage impedance of the distribution transformer 13 is reduced. That is, as a specification of the distribution transformer 13, the winding resistance is reduced (within% Z, within several percent), one leakage inductance is increased, and then high-speed control is performed so as to cancel the reactive power of the load power. By setting in this way, the voltage fluctuation can be reduced only to the voltage drop (several%) due to the winding resistance and the active power.

  For example, if the leakage impedance jXt of the distribution transformer 13 is set to twice the leakage impedance jXc of the interconnection transformer, the base residual voltage of the load voltage VL at the time of a system fault is improved to about 67%. In this case, if the reactive converter 17 is not set to output reactive power from the bidirectional converter 17, the voltage drop of the load voltage VL at the normal time is 20% at maximum, but is set to output reactive power as described above. Thus, it is possible to cancel the reactive power and suppress the voltage drop at the normal time.

  Moreover, since the uninterruptible power supply 1 has a configuration including the distribution transformer 13 in advance as described above, the load 6 can be obtained even if the installation environment (system condition) of the uninterruptible power supply 1 is not investigated in advance. Therefore, it is possible to design based on the allowable decrease rate of the load voltage which is a specification of how much the decrease in the load voltage VL can be tolerated. Moreover, adjustment is almost unnecessary when the uninterruptible power supply 1 is installed in the field. Furthermore, it is not necessary for the user of the uninterruptible power supply 1 to prepare a distribution transformer according to the load. Therefore, the versatility of the uninterruptible power supply 1 is increased and can be standardized.

  Note that the uninterruptible power supply of the method proposed this time increases the loss slightly (about 2%) by the addition of the current-limiting circuit, but can achieve higher efficiency than the constant inverter type device.

  Next, operation | movement of the uninterruptible power supply 1 whole is demonstrated based on FIG.3 and FIG.4. FIG. 3 is a waveform diagram showing the transition of changes in the power supply voltage VS, the converter voltage VC, and the load voltage VL. FIG. 4 is a flowchart for explaining the operation of the uninterruptible power supply.

  The bidirectional converter 17 of the uninterruptible power supply 1 operates in an interconnected manner regardless of whether an accident such as a momentary voltage drop or a power failure occurs on the commercial power supply 5 side, and from the commercial power supply 5 during normal times (ta to tb). Electric power is supplied to the load (s1). When an accident occurs on the commercial power source 5 side (s2, tb), based on the converter voltage VC, the residual voltage ΔVt generated according to the ratio of the leakage impedance of the distribution transformer 13 and the interconnection transformer 18, The voltage obtained by adding the circuit voltage ΔVdc is supplied to the load as the load voltage VL. During the period when ΔVdc≈0, the ratio of the leakage impedance of the distribution transformer 13 and the interconnection transformer 18 depends on the ratio. The resulting residual voltage ΔVt is supplied to the load as the load voltage VL (s3, tb to tc).

  When the uninterruptible power supply 1 detects a voltage drop with a delay within several msec by the internal control unit 12 (s4), it immediately turns off the thyristors 21a and 21b of the current limiting circuit and disconnects the system (s5). At this time, current recirculation occurs in the DC reactor 22 and the diodes 21c and 21d.

  Further, the uninterruptible power supply 1 supplies the full power of the load 6 from the bidirectional converter 17 during the period from when the accident occurs on the commercial power supply 5 side until the thyristor is turned on again (s6, tc to te). ).

  On the other hand, when the commercial power source 5 recovers from a system fault and recovers power (s7, td), the control unit 12 detects the voltage recovery of the system feeder 4 and adjusts the converter voltage VC to the phase of the power source voltage VS. (S8). Then, the controller 12 turns on the thyristors 21a and 21b to connect the commercial power supply 5 and the load 6 at the stage where the converter voltage VC and the power supply voltage VS are in phase (s9, te). Moreover, the control part 12 switches the bidirectional | two-way converter 17 to a grid operation (s10), performs a normal operation, and prepares for compensation of the next instantaneous voltage drop or a power failure (s1).

[Second Embodiment]
Next, an uninterruptible power supply according to a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing a schematic configuration of the uninterruptible power supply according to the second embodiment of the present invention.

  The uninterruptible power supply 7 shown in FIG. 5 is obtained by replacing the current limiting circuit 15 of the uninterruptible power supply 1 with a current limiting circuit 31, and the other configuration is exactly the same as the uninterruptible power supply 1. Therefore, the same parts are denoted by the same reference numerals and detailed description thereof is omitted.

  The current limiting circuit 31 includes four (two pairs) diodes 32a, 32b, 32c, and 32d, and includes two AC terminals 32a1 and 32a2 and two DC terminals 32d1 and 32d2. The anode of the diode 32a and the cathode of the diode 32b are connected to the AC terminal 32a1, and the cathode of the diode 32c and the anode of the diode 32d are connected to the AC terminal 32a2. Further, the cathode of the diode 32a and the cathode of the diode 32d are connected to the DC terminal 32d1, and the anode of the diode 32b and the anode of the diode 32c are connected to the DC terminal 32d2. Further, a DC reactor 33 and a transistor 34 as a switching element are connected in series between the DC terminal 32d1 and the DC terminal 32d2. A diode 35 whose cathode is connected to the DC terminal 32d1 is connected in parallel with the DC reactor 33.

  Since the uninterruptible power supply 7 uses a transistor, which is a self-extinguishing element, as a switching element, a point limiting circuit 15 using a thyristor having no self-extinguishing capability shown in FIG. Even when the arc signal is turned OFF, the load current becomes zero and no time is required until the arc is extinguished. Therefore, it is possible to further shorten the time from detection of an accident on the commercial power supply 5 side to turning off the transistor 34 of the current limiting circuit 31 and disconnecting the system. Moreover, since the electric current which flows through structural members, such as a DC reactor and a diode, can be suppressed by this, current capacity of each structural member, the battery 16, the bidirectional | two-way converter 17, etc. can be set small.

  Further, by providing the diode 35 in parallel with the DC reactor 33, the current Idc flowing through the DC reactor 33 can be returned even when the transistor 34 is turned off, so that overvoltage in the DC reactor 33 is suppressed. can do.

  Here, in the current limiting circuit 31 shown in FIG. 5, the case where the transistor 34 is used has been described as an example. However, the present invention is not limited to this configuration, and may be a self-extinguishing type switching element. For example, other switching elements can be used. For example, FET, GTO, IGBT, IEGT, IGCT or the like may be used instead of the transistor.

  FIG. 6 is a circuit diagram showing another configuration of the current limiting circuit. If the purpose of providing the uninterruptible power supply is to prevent an instantaneous voltage drop with respect to the load 6, the current limiting circuit 31 may not be able to completely cut off the current. In this case, a resistor (current limiting resistor) R is provided in parallel with the transistor 34 as shown in FIG. 6A, or a capacitor C is provided in parallel with the transistor 34 as shown in FIG. 6B. The configuration is as follows. Simultaneously with detecting the instantaneous voltage drop, the transistor 34 is opened, and the current Idc is limited by the DC reactor 33 and the resistor R or the DC reactor 33 and the capacitor C to prevent the instantaneous voltage drop.

[Third Embodiment]
Next, an uninterruptible power supply according to a third embodiment of the present invention will be described. FIG. 7 is a block diagram showing a schematic configuration of the uninterruptible power supply according to the third embodiment of the present invention.

  An uninterruptible power supply 8 shown in FIG. 7 is obtained by replacing the distribution transformer 13 of the uninterruptible power supply 1 with an AC reactor 41, and the other configuration is exactly the same as the uninterruptible power supply 1. Therefore, the same parts are denoted by the same reference numerals and detailed description thereof is omitted.

  As shown in FIG. 7, when the user prepares the distribution transformer 9 on the commercial power supply 5 side, the uninterruptible power supply device 1 shown in FIG. 1 cannot be used. In such a case, the same effect as that of the first embodiment can be obtained by using the uninterruptible power supply 8 having the configuration in which the AC reactor 41 is provided on the primary side of the current limiting circuit 15. That is, by providing an AC reactor having an AC impedance of jXt as the AC reactor 41 of the uninterruptible power supply 8, when an accident occurs on the commercial power supply 5 side, the AC impedance of the AC reactor 41 is linked to the AC voltage based on the converter voltage VC. The residual voltage ΔVt generated according to the ratio of the leakage impedance of the transformer 18 or a voltage obtained by adding the residual voltage ΔVt and the voltage ΔVdc of the current limiting circuit can be supplied to the load as the load voltage VL. In addition, depending on the location of the accident on the commercial power supply 5 side, the leakage impedance of the distribution transformer 9 prepared by the user can be used to prevent the load voltage VL from being lowered. Is possible.

  The uninterruptible power supply 8 is not limited to the configuration shown in FIG. 7. For example, a configuration using the current limiting circuit 31 of the uninterruptible power supply 7 instead of the current limiting circuit 15 may be used. In the case of this configuration, instead of the transistor 34, another self-extinguishing switching element may be used as described above.

It is a schematic block diagram and an equivalent circuit diagram of the uninterruptible power supply according to the first embodiment of the present invention. It is a wave form diagram which shows the change of the electric current and voltage of each part before and behind the occurrence of the accident by the commercial power source side. It is a wave form diagram which shows transition of the change of the power supply voltage VS, the converter voltage VC, and the load voltage VL. It is a flowchart for demonstrating operation | movement of an uninterruptible power supply. It is a block diagram which shows schematic structure of the uninterruptible power supply which concerns on 2nd Embodiment of this invention. It is the circuit diagram which showed another structure of the current limiting circuit. It is a block diagram which shows schematic structure of the uninterruptible power supply which concerns on 3rd Embodiment of this invention.

Explanation of symbols

1,7,8-Uninterruptible power supply 2-input terminal 3-output terminal 4-system feeder 5-commercial power supply 6-load 9,13-distribution transformer 11-instrument transformer 12-control unit 14-cut off 15-current limiting circuit 16-battery 17-bidirectional converter 18-interconnection transformer 19-breaker

Claims (6)

Accident detection means for detecting an abnormality in which the voltage of the commercial power supply decreases,
A distribution transformer that transforms a high voltage distributed from the commercial power source into a low voltage that is distributed to a load;
A current-limiting reactor that limits current when an abnormality occurs in the commercial power source, and the commercial power source and the load are connected via the current-limiting reactor when the commercial power source is normal. A high-speed switching means for cutting off the connection between the commercial power supply and the load when an abnormality is detected in the power supply; and a current flowing through the current-limiting reactor when an abnormality occurs in the commercial power supply and after the high-speed switching means is cut off. Recirculation means for recirculation, and high-speed current limiting interrupting means connected to the low voltage side of the distribution transformer,
An interconnection transformer connected in parallel with the load between the high-speed current limiting interrupting means and the load;
Power storage means for storing electric power to be supplied to the load when the commercial power supply is abnormal;
Power conversion means connected between the interconnection transformer and the power storage means, and immediately after the occurrence of an abnormality in the commercial power supply, converts the stored power of the power storage means into AC power and distributes the power to the interconnection transformer; With
The ratio of the sum of the leakage impedance of the distribution transformer and the leakage impedance of the interconnection transformer and the leakage impedance of the interconnection transformer is set to be equal to or less than an allowable reduction rate of the load voltage. An uninterruptible power supply.   The uninterruptible power supply according to claim 1, wherein the power conversion means supplies reactive power that cancels reactive power of the load when the commercial power supply is normal.   The high-speed current limiting interrupting means connects the current-limiting reactor between two DC terminals of a single-phase rectifier bridge circuit including a pair of thyristors as the high-speed switching means and a pair of diodes as the reflux means. The uninterruptible power supply according to claim 1 or 2, which has a configuration as described above.   The high-speed current limiting interrupting means is configured such that the current-limiting reactor and the self-extinguishing switching element as the high-speed switching means are connected in series between two DC terminals of the single-phase rectifier bridge circuit, The uninterruptible power supply according to claim 1 or 2, wherein a certain reflux diode is connected in parallel to the current-limiting reactor.   The uninterruptible power supply according to claim 4, wherein a current limiting resistor or a capacitor is connected in parallel to the high-speed switching means.   The uninterruptible power supply according to any one of claims 1 to 5, wherein a current-limiting reactor is provided in place of the distribution transformer.

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