JP4054749B2 - Uninterruptible power system - Google Patents

Description

  The present invention relates to an uninterruptible power supply (hereinafter referred to as UPS: Uninterruptible Power Supply).

  In a power system, a short circuit accident or an open accident may occur due to a natural or human cause, and a power failure or a voltage drop may occur. The occurrence of a power failure has a significant impact on important loads such as information equipment, communication equipment, medical electronic equipment, etc. that dislike information loss. In order to avoid such power supply troubles, many large buildings, public facilities, etc. are provided with UPSs that compensate the power supply at the time of power failure or voltage drop.

  As a conventional UPS, a parallel transformer inserted in parallel to a power supply line provided between a commercial AC input power supply and a load, a parallel compensation converter connected to the parallel transformer, and a power supply line connected in series 2. Description of the Related Art A series transformer is known which includes a series transformer, a series compensation inverter connected to the series transformer, and a power storage device connected between the parallel compensation converter and the series compensation inverter (for example, Patent Document 1). And 2).

  The conventional UPS supplies AC power supplied from a commercial AC input power source to a load via a series transformer at the same time, and at the same time converts the input AC power into DC power by a parallel compensation converter and serves as a power storage device. When the voltage drop occurs instantaneously on the AC input power supply side, the DC power stored in the power storage device is converted into AC power by the series compensation inverter and output to the series transformer, and the voltage drops via the series transformer. By injecting a compensation voltage corresponding to a minute, a power failure and a voltage drop are compensated.

In the above conventional UPS, when an AC input voltage drop due to an AC input power supply short circuit accident or an open accident or an overload or overcurrent of the parallel compensation converter is detected, the AC input power supply and the UPS are disconnected. A switch or shut-off switch is provided. According to this UPS, when a power failure occurs, the cut-off switch is opened to disconnect the AC input power supply and the UPS, and the parallel compensation converter is switched to the reverse converter operation that converts DC power into AC power, that is, the inverter operation. Power is supplied.
JP 2001-128390 A JP 2001-286078 A

  However, the cut-off switch provided in the conventional UPS (Patent Documents 1 and 2) has several tens of minutes from the detection of a voltage drop or the like to the complete disconnection of the AC input power source and the UPS because of its operating characteristics. It has a delay time of msec. During this delay time, the path between the UPS and the location where the short circuit accident occurred in the power system is in a connected state, and a large current flows from the UPS side toward the location where the short circuit accident occurred. As a result, there is a possibility that the UPS is exposed to overcurrent and stops, and smooth power supply compensation cannot be performed. In order to prevent this, there is a method of providing a high-speed switch such as a thyristor, but power loss occurs in a steady state and is expensive.

  An object of the present invention is to provide an uninterruptible power supply capable of protecting a UPS from an overcurrent without using a high-speed switch when an input is short-circuited and capable of supplying stable power to a load without instantaneous interruption. is there.

In order to solve the above problem, the invention according to claim 1 is configured such that one end of a switch (for example, switch 3 of FIG. 1) is connected to an AC input power supply (for example, AC input power supply 1 of FIG. 1), An uninterruptible power supply (for example, UPS 100 in FIG. 1) connected between the other end of the switch and a load (for example, load 2 in FIG. 1), and a power storage device (for example, in FIG. 1) A power storage device 5), a power line connected to the switch and supplying AC input power supplied from the AC input power source to a load (for example, the power line 4 in FIG. 1), and the other end of the switch The AC input voltage detector (for example, the converter control device 7 in FIG. 1) for detecting the AC input voltage is connected to the power supply line via a reactor (for example, the reactor 11 in FIG. 1), and the AC input power is This is converted to DC power It is composed of a power conversion element that switches between a converter operation that outputs power to a power storage device and an inverter operation that converts DC power stored in the power storage device into AC power and outputs it to the power line. A bidirectional converter (for example, the bidirectional converter 6 in FIG. 1), an inverter (for example, the inverter 8 in FIG. 1) that converts DC power stored in the power storage device into AC power, and outputs the AC power; An injection transformer (for example, the transformer 10 in FIG. 1) connected in series to the power supply line and injecting AC power output from the inverter into the power supply line, and a load supply voltage for detecting the AC voltage supplied to the load The AC voltage detected by the detector (for example, the inverter control device 9 in FIG. 1) and the load supply voltage detector is always the load rated voltage. Inverter control means for controlling the output of the inverter (for example, the inverter control device 9 in FIG. 1) and a current detector for detecting the current flowing in the AC side of the bidirectional converter (for example, in FIG. The AC output voltage (for example, V ₂ in FIG. 1) of the bidirectional converter is changed to the AC input voltage (for example, the voltage in FIG. 1) until the switch is opened when the current detector 13) and the input are short-circuited. The two are controlled so as to prevent the overcurrent from flowing from the bidirectional converter to the AC input power supply by narrowing down according to the voltage at the detection end 12 and performing the inverter operation with a soft start after the opening of the switch. A bidirectional converter control means for controlling the directional converter (for example, the converter control device 7 in FIG. 1), and a load (for example, the load in FIG. 1) when the input is short-circuited. 2) is characterized in that power is supplied without interruption.

  According to the first aspect of the present invention, when the bidirectional converter detects an overcurrent, the converter control means causes the converter command value so that the AC output voltage of the bidirectional converter becomes equal to the AC input voltage. Is calculated from the DC voltage and the AC voltage, and the control command value is given to the bidirectional converter, thereby preventing the occurrence of overcurrent. For this reason, when a short-circuit accident occurs in the AC input power supply, even if a connection state is established in the path between the uninterruptible power supply and the AC input power supply short-circuit occurrence location, the uninterruptible power supply side changes from Therefore, it is possible to prevent a large current from flowing and prevent the uninterruptible power supply from being stopped. During this time, the inverter supplies the load rated voltage to the load via the injection transformer by the inverter control means, so that stable power can be supplied to the load without power failure even in the event of a power failure due to a short-circuit accident of the AC input power supply.

Embodiments of a UPS according to the present invention will be described below with reference to the drawings.
First, an outline of the UPS 100 according to the present invention is shown in FIG. As shown in FIG. 1, a switch 3 is interposed between an AC input power source 1 and a load 2 from the power system. One end of the switch 3 is connected to the AC input power source 1 side, and the other end is connected to the load 2 side. Hereinafter, the wiring between the switch 3 and the load 2 is referred to as a power line 4 for convenience. A power converter 101 and an instantaneous voltage drop compensator 102 are connected to the power line 4.

  The power conversion device 101 converts the AC voltage supplied from the AC input power source 1 through the switch 3 into a DC voltage and supplies it to the power storage device 5, and the stored power of the power storage device 5 as AC power. A bidirectional converter 6 composed of a power conversion element capable of switching between an inverter operation that is converted into an inverter and supplied to a load 2, and a converter control device 7 that controls the bidirectional converter 6.

  The instantaneous voltage drop compensator 102 also converts the stored power of the power storage device 5 into AC voltage, the inverter control device 9 that controls the inverter 8, and the AC voltage output from the inverter 8 as a predetermined value. And an injection transformer 10 that injects the transformed AC voltage into the AC input voltage and supplies the AC voltage to the load 2.

  The power conversion device 101 supplies the AC power source 1 to the load 2 at the normal time, converts the AC power into DC power by the power conversion device 101, and stores it in the power storage device 5. The voltage drop generated in the power supply line 4 at this time is supplied and compensated by the instantaneous voltage drop compensator 102 so as to compensate the shortage by converting the stored power of the power storage device 5 into AC power.

  When an abnormality such as a short circuit accident occurs in the power system or the AC input power source 1, the power conversion device 101 converts the stored power of the power storage device 5 into AC power, and the converted AC power is replaced with the AC input power source 1 as a power line. 4 is supplied. At this time, the switch 3 is opened, but as described above, there is a delay until the disconnection is completed due to the operating characteristics of the switch 3. An overcurrent is about to occur on the AC input power supply 1 side. Therefore, the UPS 100 according to the present invention is configured to effectively prevent the occurrence of overcurrent by the converter control device 7 provided in the power conversion device 101. Details thereof will be described later.

Next, each component of the UPS 100 will be described.
The switch 3 is composed of, for example, an electromagnetic contactor or a thyristor switch, one end of which is connected to the AC input power source 1 and the other end is connected to the input end of the bidirectional converter 6 and the primary side of the injection transformer 10.
Normally, the switch 3 is closed, and the AC input voltage V ₁ supplied from the AC input power source 1 is supplied to the load 2 via the injection transformer 10.

Further, when the AC input voltage V ₁ falls below a preset reference value, a switch opening command signal is supplied to the switch 3 from the converter control device 7 described later. When this opening command signal is received, the switch 3 is opened. When the switch 3 is completely opened, the switch 3 outputs a switch open answerback signal to the converter control device 7.

  A main circuit device (that is, a power conversion element) of the bidirectional converter 6 is configured using, for example, an IGBT (Insulated Gate Bipolar Transistor). The AC side input / output terminal of the bidirectional converter 6 is connected in parallel to the power supply line 4 through the reactor 11, and the DC side input / output terminal is connected to the power storage device 5 and the input terminal of the inverter 8.

The bidirectional converter 6 is normally controlled so that the voltage of the power storage device 5 is constant, and performs a converter operation for converting an AC input voltage into a DC voltage and outputting it to the power storage device 5 or the inverter 8. . When the AC input voltage V ₁ detected via the voltage detection terminal 12 falls below a predetermined reference value, the bidirectional converter 6 is controlled so as to suppress the current without stopping by overcurrent protection. After confirming that the switch 3 is opened, an inverter operation for converting the DC voltage stored in the power storage device 5 into an AC voltage is performed by soft start. The converted AC voltage is supplied to the power supply line 4 via the reactor 11. These converter operation and inverter operation and switching between the converter operation and the inverter operation are controlled by a converter control device 7 which will be described later.

Between the bidirectional converter 6 and the reactor 11, a current detector 13 composed of, for example, a current transformer (CT) is connected. The current detector 13 detects an alternating current I ₁ flowing through the reactor 11 and is a constituent element of the converter control device 7 described below.

  In the present embodiment, converter control device 7 is realized by computer control, and cooperation between a control program stored in a storage device such as ROM (not shown) and a CPU (not shown). To generate a control signal for the bidirectional converter 6. The converter control device 7 can also be configured by an analog control circuit using an operational amplifier.

  Since the control content of the converter control device 7 is different between a normal time (converter operation) and a power failure or voltage drop (inverter operation), the following description will be made separately for each operation.

FIG. 2 shows a control element block diagram of the converter control device 7 during the converter operation. In FIG. 2, an AC input voltage detection signal V ₁ , an AC input current detection signal I _1, and a DC voltage detection signal V _{5 of the} power storage device ₅ are input to the converter control device 7. The AC input voltage signal V ₁ is captured from the voltage detection terminal 12, the AC input current detection signal I ₁ is captured from the current detector 13, and the DC voltage detection signal V ₅ is captured from the voltage detection terminal 14 (see FIG. 1). .

Since the output DC voltage V ₅ of the electric power storage device 5 must always be kept constant, the converter control unit 7 is given a DC voltage command value Vr, the DC voltage command value Vr in comparison element 71, It is compared with the DC voltage detection signal V _5. The comparison output, that is, the difference signal V ₇₁ between V ₅ and Vr is input to the power factor control and V ₅ constant voltage control element 72.

The AC input voltage detection signal V ₁ is given to the phase detection element 73. The phase detection signal V ₇₃ is input to the power factor control and V ₅ constant voltage control element 72.
The power factor control and V ₅ constant voltage control element 72 generates a power factor control and V ₅ constant voltage control signal V ₇₂ based on the difference signal V ₇₁ , the phase detection signal V ₇₃ and the AC input current detection signal I _1. , To the addition element 74.

The addition element 74 performs an addition operation (V ₁ + V ₇₂ ) between the AC power supply voltage V ₁ and the power factor control and V ₅ constant voltage control signal V _72, and sends the addition signal to the multiplication element 75.
The multiplication element 75 multiplies the addition operation value (V ₁ + V ₇₂ ) by the coefficient signal V ₇₆ from the coefficient element 76 (substantially divides by the DC voltage detection value V ₅ ), and the multiplication signal V _75. Is applied to the PWM modulator 77.

The PWM modulator 77 generates a modulation control signal V ₇₇ based on the multiplication signal V ₇₅ and supplies the modulation control signal V ₇₇ to the gate of the power conversion element constituting the bidirectional converter 6. As a result, the bidirectional converter 6 supplies appropriate power to the power storage device 5.

On the other hand, during the converter operation, the AC input voltage V ₁ and the AC input current I ₁ are constantly monitored by the AC input voltage detection element 78 and the current detector 13, and if there is no abnormality such as a power failure or a voltage drop, a power failure is short-circuited. There is no signal output from the sensing element 79. Thus, switch 3 is closed, short-circuit detection signal V ₈₀ is not output.

When the AC voltage detection signal V ₁ detected from the AC voltage detection terminal 12 falls below the reference value, that is, when an abnormality such as a power failure occurs, an open command signal V ₇₉ is output from the power failure short-circuit detection element 79 to open and close The vessel 3 is opened. Further, when the current detector 13 detects a current I _{1 that} is equal to or greater than the reference value, an open command signal V ₇₉ is also output from the power failure short-circuit detecting element 79 to the switch 3, and the switch 3 is opened. When the switch 3 is opened, the bidirectional converter 6 performs an inverter operation.

Here, FIG. 3 shows a control element block diagram of the bidirectional converter 6 during inverter operation. In FIG. 3, the DC voltage detection signal V ₅ of the power storage device ₅ is input to the converter control device 7. This DC voltage detection signal V ₅ is taken in from the voltage detection terminal 14 as in the converter operation (see FIG. 1).

The phase angle generation element 81 generates a phase angle generation signal V ₈₁ based on the clock pulse signal V ₈₂ input from the oscillator 82 and sends it to the sine wave generation element 83. The sine wave generation element 83 generates a sine wave generation signal V ₈₃ based on the phase angle generation signal V ₈₁ and sends it to the multiplication element 75.

The multiplication element 75 multiplies the sine wave generation signal V ₈₃ by the coefficient signal V _{76 ′} from the coefficient element 76 and supplies the multiplication signal V _{75 ′} to the PWM modulator 77. The PWM modulator 77 generates a modulation control signal V _{77 ′} based on the multiplication signal V _{75 ′} and supplies the modulation control signal V _{77 ′} to the gate of the power conversion element constituting the bidirectional converter 6.

  The power storage device 5 is composed of, for example, an electric double layer capacitor, a storage battery, and the like, and is supplied with a constant voltage from the bidirectional converter 6 and stores DC power. Then, at the time of a power failure or the like, the stored DC power is released by the inverter operation of the bidirectional converter 6.

  The inverter 8 has an input terminal connected to the DC input / output terminal of the bidirectional converter 6 and the power storage device 5, and an output terminal connected to the primary side of the injection transformer 10. Then, the DC voltage supplied from bidirectional converter 6 or power storage device 5 is converted into an AC voltage, and the converted AC voltage is output to the primary side of injection transformer 10.

The main circuit device (that is, the power conversion element) of the inverter 8 is configured using, for example, an IGBT similarly to the bidirectional converter 6. The operation of the inverter 8 is controlled by the inverter control device 9, and the output of the inverter 8 is controlled so that the load side AC voltage V ₄ detected via the AC voltage detection terminal 15 always becomes the load rated voltage.

  In the present embodiment, the inverter control device 9 is embodied by computer control in the same manner as the converter control device 7, and includes a control program and a CPU (see FIG. 5) stored in a storage device such as a ROM (not shown). The control signal of the inverter 8 is generated in cooperation with (not shown). The inverter control device 9 can also be configured by an analog control circuit.

FIG. 4 shows a control element block diagram of the inverter control device 9.
In FIG. 4, a DC voltage detection signal V ₅ , an AC voltage detection signal V ₂ , and an AC voltage detection signal V ₄ are input to the inverter control device 9. The AC input voltage signal V ₂ is supplied to the phase detection element 91, and the phase (for example, 50 Hz) required for the control output V ₉₂ of the PWM modulator 92 is detected. The phase detection signal V ₉₁ is input to the sine wave generation element 93. The sine wave generation element 93 generates a sine wave generation signal V ₉₃ based on the input phase detection signal V ₉₁ .

The V ₄ constant voltage control element 94 generates a V ₄ constant voltage control signal V ₉₄ based on the AC voltage detection signal V ₂ , the AC voltage detection signal V ₄ , and the sine wave generation signal V ₉₃ and sends it to the multiplication element 95. The multiplication element 95 multiplies the V ₄ constant voltage control signal V ₉₄ by the coefficient element V ₉₆ and supplies the multiplication signal V ₉₅ to the PWM modulator 92.

Based on the multiplication signal V ₉₅ , the PWM modulator 92 generates a modulation signal V ₉₂ for controlling to a constant voltage having a phase required for the power supplied to the load 2. Supply to the gate. As a result, the inverter 8 supplies appropriate power to the load 2 through the injection transformer 10.

The injection transformer 10 has a primary side connected to the output terminal of the inverter 8 and a secondary side connected between the AC power source 1 and the load 2. Then, the output voltage of the inverter 8 is transformed according to the winding ratio between the primary side and the secondary side, and the AC input voltage V ₁ supplied from the AC input power source ₁ or the converter AC supplied from the bidirectional converter 6. adding the injection voltage V ₃ after the transformer on the side voltage V _2, it is maintained constant at all times the level of the load-side AC voltage V ₄ is supplied to the load 2.

Next, the operation of the UPS 100 will be described with reference to FIGS.
First, the normal operation will be described. During normal times, that is, while power is being supplied from the AC input power supply 1 (until timing T ₁ shown in FIG. 6), the switch 3 is in a closed state, and the AC input voltage V ₁ is applied to the injection transformer 10. To the load 2. At this time, the bidirectional converter 6 converts the supplied AC power into DC power, and supplies the converted DC power to the power storage device 5 (see FIG. 1).

During this time, if the load-side AC voltage V ₄ detected from the AC voltage detection terminal 15 does not reach the rated load voltage due to an instantaneous drop or fluctuation of the AC input voltage V ₁ , the inverter 8 is released from the power storage device 5. The AC power corresponding to the shortage is generated from the DC power, and the injection voltage V ₃ is injected through the injection transformer 10. The injection voltage V ₃ is added to the AC input voltage V ₁ , and the load side AC voltage V ₄ supplied to the load 2 is always kept constant as shown in FIG. Accordingly, the AC load current I ₂ supplied to the load ₂ is always kept constant.

Next, the operation at the time of a power failure caused by the occurrence of a short circuit accident or the like will be described.
Here, at the timing of T ₁ shown in FIG. 6, as a two-wire short-circuit fault in the AC input power source 1 side has occurred it will be described below.

When a two-wire short circuit accident occurs, the voltage at the voltage detection terminal 12 decreases. This decrease in the AC input voltage V ₁ is detected by the AC input voltage detection element 78. Based on this detection signal, the converter control device 7 causes the power failure / short-circuit detection element 79 to supply a switch opening command signal to the switch 3 (step S1).

At the same time, since the load side AC voltage V ₄ detected from the AC voltage detection terminal 15 decreases, the inverter control device 9 increases the output of the inverter 8 and the AC voltage corresponding to the load rated voltage via the injection transformer 10. Is supplied to the load 2.

During this time, if the alternating current I ₁ flowing from the bidirectional converter 6 side toward the alternating current input power source 1 exceeds the reference value (step S2: Y), the converter alternating voltage V ₂ output from the bidirectional converter 6 is obtained. Is reduced according to the AC input voltage detected at the AC voltage detection end 12 to prevent an overcurrent from flowing from the bidirectional converter 6 toward the AC input power source 1. Specifically, the power factor control and V5 constant voltage control element 72 is supplied from the power failure short circuit detection element 79 to the power factor control and V5 constant voltage control element 72, and the power factor control and V5 constant voltage control element 72 performs power factor control and V5 constant voltage control. It stopped (step S3), and the power factor control and V5 constant voltage control signal V ₇₂ to zero. As a result, the bidirectional converter 6 outputs a converter AC side voltage V ₂ that is equal to the AC power supply voltage V _1, and the current I ₁ becomes substantially zero. As a result, the overcurrent of the current I ₁ can be prevented as shown in FIG.

Next, in step S4, based on the answerback signal from the switch 3, it is confirmed whether or not the switch 3 is completely opened. For example, when the switch 3 at the timing T ₂ shown in FIG. 6 verify that it is fully opened (step S4: Y), converter control unit 7 changes the bidirectional converter 6 to the inverter operation, the inverter operation (See FIG. 3).

When the bidirectional converter 6 is activated by the inverter operation at the timing T ₂ , the bidirectional converter 6 is gradually output voltage (V ₂ ) by the soft start control by the converter controller 7 as shown in FIG. I will raise. This output voltage is supplied to the load 2 via the power line 4. Along with this, the injection voltage V ₃ injected by the inverter 8 through the injection transformer 10 gradually decreases. As described above, the load-side AC voltage V ₄ is always the load rated voltage between the timings T ₁ and T ₂ and after the timing T ₂ , and the rated voltage equal to that before the occurrence of the short-circuit accident is supplied to the load 2.

Note that even if a decrease in the AC input voltage V ₁ is detected, an overcurrent is not reached, and an overcurrent may not be detected (step S2: N). In this case, when it is confirmed that the switch 3 is completely opened (step S5: Y), the converter control device 7 switches the operation of the bidirectional converter 6 from the converter operation to the inverter operation. Thus, bidirectional converter 6 performs an inverter operation and supplies AC power to load 2.

According to the UPS 100 described above, when the bidirectional converter 6 detects an overcurrent, the converter AC side voltage V ₂ output from the bidirectional converter 6 by the converter control device 7 is equal to the AC input voltage V ₁ . It is possible to prevent the occurrence of overcurrent by calculating converter command values that are equal to each other from the DC voltage and the AC voltage and giving the control command value to the bidirectional converter 6. For this reason, when a short-circuit accident occurs in the AC input power supply 1, even if a connection state is established in the path between the UPS 100 and the short-circuit occurrence location on the AC input power supply 1 side, the converter control device 7 causes a short-circuit accident from the UPS 100 side. It is possible to prevent a large current from flowing toward the generation point and to prevent the UPS 100 from stopping. During this time, the inverter 8 supplies the load rated voltage to the load 2 via the injection transformer 10 by the inverter control device 9, so that stable power can be supplied without interruption in the event of a power failure due to a short circuit accident of the AC input power supply 1. Can be supplied to.

It is a block diagram which shows the functional structure of the uninterruptible power supply of embodiment which applied this invention. It is a control element block diagram when the converter control apparatus shown in FIG. 1 makes a bidirectional converter perform converter operation. It is a control element block diagram when the converter control apparatus shown in FIG. 1 makes a bidirectional | two-way converter perform inverter operation | movement. It is a control element block diagram of the inverter control apparatus of FIG. It is a flowchart which shows the process sequence when the converter control apparatus of FIG. 1 detects the voltage drop of alternating current input power supply. It is the timing chart which showed the waveform of the voltage or electric current in each position of the uninterruptible power supply device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC input power supply 2 Load 3 Switch 4 Power supply line 5 Power storage device 6 Bidirectional converter 7 Converter control device 8 Inverter 9 Inverter control device 10 Injection transformer 11 Reactor 12 AC voltage detection end 13 Current detector 14 DC voltage detection end 15 AC voltage detection terminal 100 Uninterruptible power supply 101 Power converter 102 Instantaneous voltage drop compensation device V ₁ AC input voltage V ₂ Converter AC side voltage V ₃ Injection voltage V ₄ Load side AC voltage V ₅ DC voltage

Claims (1)

An uninterruptible power supply device in which one end of a switch is connected to an AC input power source and connected between the other end of the switch and a load,
A power storage device;
A power line connected to the switch and supplying AC input power supplied from the AC input power source to a load;
An AC input voltage detector for detecting the AC input voltage at the other end of the switch;
A converter operation connected to the power supply line via a reactor, converting the AC input power into DC power, and outputting the DC power to the power storage device, and the DC power stored in the power storage device as AC power A bidirectional converter composed of a power conversion element capable of switching between an inverter operation to be converted into an output to the power supply line, and
An inverter that converts DC power stored in the power storage device into AC power and outputs the AC power;
An injection transformer connected in series to the power supply line and injecting AC power output from the inverter into the power supply line;
A load supply voltage detector for detecting an alternating voltage supplied to the load;
Inverter control means for controlling the output of the inverter so that the AC voltage detected by the load supply voltage detector is always a load rated voltage;
A current detector for detecting a current flowing on the AC side of the bidirectional converter;
Until the switch is opened in the event of an input short circuit, overcurrent flows from the bidirectional converter toward the AC input power supply by narrowing the AC output voltage of the bidirectional converter according to the AC input voltage. A bidirectional converter control means for controlling and controlling the bidirectional converter to perform the inverter operation with a soft start after releasing the switch;
With
An uninterruptible power supply that supplies power to a load without interruption in the event of an input short circuit.

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