JP7310766B2 - power conversion system - Google Patents

Description

The present invention relates to power conversion systems.

2. Description of the Related Art Recently, uninterruptible power supply systems (UPS) using power semiconductors have been increasingly applied to plants and the like as countermeasures against momentary power failures due to lightning and the like. Moreover, in recent years, the number of cases where a large AC motor is soft-started using a power converter is increasing.

For example, Patent Literature 1 discloses a phase synchronization process at the time of power recovery in an uninterruptible power supply of a constant commercial power supply system.

JP 2009-273206 A

Conventionally, in a system that supplies power to the motor and the critical load from the same commercial power supply, a power converter for soft start is used to start the motor, and then power is supplied directly from the commercial power supply to the critical load. In the case of supplying power via an uninterruptible power supply as a countermeasure against voltage drops, the power converter was not used after the motor was synchronously connected to the commercial power supply.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power conversion system capable of soft-starting a motor and compensating for a voltage drop to a load device with a simple configuration.

A power conversion system according to an aspect of the present invention includes a power conversion device connected to be able to receive power from an AC power supply, a second switch that connects or disconnects the output of the power conversion device to or from an electric motor, and the AC power supply. A first switch that connects or disconnects the electric motor, a third switch that connects or disconnects the AC power supply to the load device, and connects or disconnects the output of the power conversion device to the load device A fourth switch that shuts off and a control unit are provided, and the control unit, in a state in which the second switch and the third switch are closed and a state in which the first switch and the fourth switch are open, Power is supplied from the power conversion device to the electric motor, the electric motor is started, and after the electric motor reaches a predetermined speed, the first switch is closed to connect the electric motor to the AC power supply, and the electric motor is is capable of receiving power directly from the AC power supply, then cuts off the second switch, then closes the fourth switch to supply power to the load device from the power conversion device, and then , the third switch is cut off, and the power conversion device is caused to perform a voltage sag compensation operation.

Further, a power conversion system according to an aspect of the present invention includes a power conversion device connected to be able to receive power from an AC power supply, a second switch that connects or disconnects the output of the power conversion device to or from the electric motor, A first switch that connects or disconnects an AC power supply to or from the electric motor, a third switch that connects or disconnects the AC power supply to or from a load device, and a switch that connects or disconnects the output of the power conversion device to the load device. A fourth switch that connects or disconnects, and a controller, wherein the controller controls a state in which the second switch and the third switch are closed and a state in which the first switch and the fourth switch are open. supplying power from the power conversion device to the electric motor, starting the electric motor, and after the electric motor reaches a predetermined speed, closing the first switch to connect the electric motor to the AC power supply; After enabling the electric motor to receive power directly from the AC power supply, the fourth switch is closed to supply power from the power conversion device to the load device, and then the second switch and the third switch. It is characterized in that the switch is cut off and the power conversion device is operated to compensate for the voltage sag.

According to the present invention, it is possible to realize motor starting (soft start) and momentary sag compensation for important loads with a simple configuration.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which illustrates the power conversion system concerning one Embodiment, and its periphery. It is a figure which shows the structural example of an inverter control part. 4 is a timing chart showing a first operation example of the power conversion system according to one embodiment; It is a flow chart which shows the example of the 1st operation of the power conversion system concerning one embodiment. 4 is a timing chart showing a second operation example of the force conversion system according to one embodiment;

A power conversion system according to an embodiment of the present invention will be described. FIG. 1 is a diagram illustrating a power conversion system 1 and its periphery according to one embodiment. A power conversion system 1 supplies power from a three-phase AC power supply (commercial power supply) 2 to a motor (M) 3 and a load device 4 as an important load.

A primary side of the transformer 5 is connected to a fourth switch 40 and a fifth switch 50 in the power conversion system 1, which will be described later. A secondary side of the transformer 5 is connected to the load device 4 . The transformer 5 transforms the power input from the primary side into a predetermined voltage and supplies it to the load device 4 .

The power conversion system 1 includes, for example, a power conversion device 6, a switch control device 7, a first switch 10 to a fifth switch 50, a first voltage detection unit 100, a second voltage detection unit 200, as shown in FIG. , a first current detection unit 300 and a second current detection unit 400 .

The input side of the power converter 6 is connected to the AC power supply 2 via the fifth switch 50 . The electric motor 3 is connected to the AC power supply 2 via the first switch 10 and is connected to the output side of the power converter 6 via the second switch 20 . That is, the electric motor 3 can receive power supply from the AC power supply 2 and can receive power supply from the power conversion device 6 . The primary side of the transformer 5 is connected to the AC power supply 2 via the third switch 30 and connected to the output side of the power converter 6 via the fourth switch 40 . That is, the load device 4 can be supplied with power from the AC power supply 2 and can be supplied with power from the power conversion device 6 via the transformer 5 .

The power conversion device 6 has a converter circuit (REC) 60 , a capacitor 61 , an inverter circuit 62 and an inverter control section 8 . The converter circuit 60 converts the input AC power into DC power and outputs it to the capacitor 61 of the DC circuit. Capacitor 61 smoothes the DC input from converter circuit 60 and outputs it to inverter circuit 62 . The inverter circuit 62 converts the DC power input from the capacitor 61 into AC power having a predetermined voltage and a predetermined frequency, and outputs the AC power. The inverter control unit 8 controls each unit constituting the power conversion device 6 and outputs control signals to the switch control device 7 .

The switch control device 7 controls the first to fifth switches 10 to 50 and outputs control signals to the inverter control section 8 .

The first voltage detection section 100 detects the voltage of the AC power supply 2 .

The second voltage detection section 200 detects the output voltage of the power conversion device 6 .

The first current detection unit 300 is installed on the electric motor 3 side of the first switch 10 and detects the electric current flowing through the electric motor 3 via the first switch 10 .

The second current detector 400 is installed on the transformer 5 side of the third switch 30 and detects the current flowing through the transformer 5 via the third switch 30 .

For example, when the switch control device 7 starts (soft-starts) the electric motor 3, the first switch 10 and the fourth switch 40 are opened, and the second switch 20, the third switch 30 and the second switch 30 are opened. 5 The switch 50 is closed. Power is supplied to the load device 4 via the third switch 30 and the transformer 5 . Acceleration of the electric motor 3 is started in this state.

The switch controller 7 controls the fourth switch 40 to close and the third switch 30 to open after the electric motor 3 reaches a predetermined rotational speed. A so-called electric motor 3 is synchronously connected to the AC power supply 2 . At this time, based on the detection result of the first voltage detection section 100 and the detection result of the second voltage detection section 200, control is performed so as to establish synchronization.

Further, after closing the first switch 10, the switch control device 7 confirms that the detection result of the first current detection unit 300 satisfies a predetermined condition, opens the second switch 20, and After closing the fourth switch 40, it is confirmed that the detection result of the second current detection unit 400 satisfies a predetermined condition, and the third switch 30 is controlled to open.

The switch control device 7 may perform the above control mutually with the inverter control section 8 or in cooperation with the inverter control section 8 .

Next, a specific example of the inverter control section 8 will be described. FIG. 2 is a diagram showing a configuration example of the inverter control section 8. As shown in FIG. As shown in FIG. 2, the inverter control unit 8 includes a motor drive unit 80, a phase synchronization unit 81, a voltage sag compensation unit 82, an inverse d/q conversion unit 83, a PWM (Pulse Width Modulation) unit 84, and the like. , and controls each unit constituting the power conversion device 6 . The d/q conversion circuit uses the phase signal as a reference and converts the input 3-phase AC signal into a two-axis component that is in-phase with the phase signal and a component that has a direct effect on the phase signal and outputs it. It is a circuit that The inverse d/q conversion circuit is a circuit that inversely converts the input phase signal, that is, inversely converts the two-axis signal into a three-phase AC signal.

The inverter control unit 8 includes changeover switches SW1a and SW2a. The changeover switches SW1a and SW2a each have an A terminal input and a B terminal input. If the B terminal input is selected, the signal from the B terminal input is output. When the A terminal input side of SW1a and SW2a is selected, the motor drive mode (motor soft start mode) is selected, and when the B terminal input is selected, the voltage sag compensation mode (voltage sag compensation for important load) is switched. It is made possible.

The inverter control unit 8 is provided with a switch SW3a and a switch SW4a. The switch SW3a and the switch SW4a output a value of 0 when the switch SW3a and the switch SW4a are open. Output the value Δf.

The electric motor driving section 80 is a circuit that generates a voltage control signal for driving the electric motor 3 when the electric motor 3 is soft-started. In the motor drive unit 80, the inverter control unit 8 generates a differential signal using a speed reference transmitted from a device (not shown) and a speed feedback ωr of the motor 3 obtained from a position sensor, angle sensor or speed sensor (not shown). A current control signal is output from the speed control circuit 801 so that the rotational speed of the motor (speed feedback ωr) follows the sum of the speed reference and the output of the switch SW3a.

In addition, the motor drive unit 80 detects the output current of the inverter circuit 62 with a current sensor (not shown), and uses the output as current feedback to convert the d/q conversion circuit 802 into a d/q conversion circuit 802 using a first reference phase signal θe, which will be described later. q-return is performed, and the difference between the output thereof and the output of the speed control circuit 801 is obtained, the result is output to the current control circuit 806, and a signal is output so that the output current of the inverter circuit 62 follows the output of the speed control circuit 801. do. The output of the current control circuit 806 is a voltage control signal in the motor drive mode, and is a signal for motor control of two orthogonal axes. The orthogonal two-axis motor control signals are inputted to the A terminal input of the switch SW1a.

Note that the motor drive unit 80 adds the calculation result of the slip computing unit 803 to the current control signal output from the speed control circuit 801 with an adder for the speed feedback ωr of the motor 3 to obtain the electric frequency ωe. The result of integrating the frequency ωe by the integrating circuit 808 is output to the A terminal input of the switch SW2a as the electrical phase angle signal θe1 in the motor driving mode. In addition, the motor drive section 80 detects that the motor 3 has reached a rotation speed that allows synchronous input to the AC power supply 2 by means of a speed level detection circuit, and outputs the result to the switch control device 7 as well. SW3a is used for phase adjustment when the motor 3 is synchronized. The slip calculator 803, the adder, the integration circuit, and the like constitute a first phase detector.

The phase synchronization unit 81 detects the phase of the power supply voltage detected by the first voltage detection unit 100 using a PLL (phase locked loop), and synchronizes the phase to each d/q conversion circuit and the inverse d/q conversion circuit. A signal is output, and a timing signal for synchronizing the switch is output to the switch control device 7 . The synchronization detector is an example of the second phase detector. For example, the phase detection circuits PLL1A and PLL2A output a first power supply phase signal θe2 and a second power supply phase signal θs synchronized with the AC power supply 2 when there is an input from the first voltage detection unit 100 . The first power supply phase signal θe2 is connected to the B terminal input of the switch SW2a.

Further, SW4a is used for phase adjustment when changing from the voltage sag compensation mode to the parallel connection of the AC power supply 2. FIG. For example, when the phase detection circuit PLL1A receives an input signal from the first voltage detection unit 100 while the SW4a is on, the phase detection circuit PLL1A synchronizes with the frequency obtained by adding the correction frequency Δf to the AC power supply 2 as the first voltage. It outputs the power supply phase signal θe2.

When there is no input to the first voltage detection section 100, that is, when the AC power supply 2 generates a voltage drop, the phase detection circuits PLL1A and PLL2A generate phase signals at a preset free-running frequency. to output Desirably, the free-running frequency is the frequency of the AC power supply 2 or a value in the vicinity thereof. Also, preferably, the phase detection circuit PLL1A has a long pull-in time constant from the free-running frequency with respect to the input signal, so that when the AC power supply 2 recovers from an instantaneous voltage drop, the phase of the AC power supply 2 and the phase Even if the phase due to the free-running frequency of the detection circuit PLL1A differs by 180 degrees, the output phase of the phase detection circuit PLL1A is set so as not to change abruptly. The permissible value for sudden change is determined, for example, from the permissible phase change value of the load device 4 and the permissible overcurrent at the time of phase change. Here, it is assumed that the phase detection circuit PLL2A has a faster pull-in time constant (response speed) than the phase detection circuit PLL1A. Here, the output of the phase detection circuit PLL1A is assumed to be the first power supply phase signal θe2, and the output of the phase detection circuit PLL2A is assumed to be the second power supply phase signal θs.

In the phase synchronization unit 81, the voltage of the AC power supply 2 detected by the first voltage detection unit 100 is d/ After q-transformation, the amplitude components of the two orthogonal axes of the AC power source 2 are extracted. Then, it is input to the reference voltage circuit 821 of the momentary sag compensator 82 . In the phase synchronization section 81, the phase comparison circuit 812 compares the second power supply phase signal θs output from the phase detection circuit PLL2A and the first reference phase signal θe output from the changeover switch SW2a, and the difference between the two is determined to be a predetermined value. If it is less than the value, it outputs to the switch control device 7 a timing signal for closing the circuit breaker at the time of synchronous entry.

In the momentary sag compensator 82, the output voltage of the power converter 6 detected by the second voltage detector 200 is d/q-converted by the d/q conversion circuit 822 with reference to the first reference phase signal θe, and the reference voltage The difference from the output of circuit 821 is input to voltage control circuit 823 . The output of the voltage control circuit 823 is a two-axis voltage control signal that is orthogonal to each other, and is connected to the B terminal input of the switch SW1a. As a result, in the voltage sag compensation mode, the B terminal input is selected as the output of the changeover switch SW1a. Controls the output of the control circuit.

Note that the reference voltage circuit 821 has a function of holding an input signal. In the non-holding state, it outputs according to the input signal, and in the holding state, it holds and continues to output the output immediately before the holding state. As will be described later, the reference voltage circuit 821 is in a holding state at time t8A after the third switch is opened, and is in a non-holding state after time t9 and before time t8A before turning on the third switch. That is, it is configured to hold and output the value before the occurrence of the voltage sag during the period when the voltage sag occurs, and to output according to the input during other periods. Therefore, stable electric power can be supplied to the load device 4 even during the momentary sag period. In order to prevent a sudden change in the output voltage when shifting from the holding state to the non-holding state, some first-order lag element (filter) may be provided on the output side of the voltage control circuit.

The inverse d/q conversion unit 83 receives the voltage control signal output from the changeover switch SW1a and performs inverse d/q conversion on the basis of the first reference phase signal θe output from the switch SW2a. A voltage command signal is generated and output to the PWM section 84 . The PWM unit 84 PWM-modulates the voltage command signal using a predetermined carrier signal, and drives the switching elements forming the inverter circuit 62 as a gate signal. With this configuration, the inverter circuit 62 can output a predetermined AC power.

Although FIG. 2 shows the configuration of the motor drive unit 80 in the case of the sensor-equipped vector control when the electric motor 3 is an induction motor, the configuration may be of sensorless vector control. Furthermore, even if the electric motor 3 is a synchronous electric motor, the electric motor driving section 80 can be realized with a similar configuration.

Next, a first operation example of the power conversion system 1 will be described with reference to FIGS. 3 and 4. FIG. FIG. 3 is a timing chart showing a first operation example of the power conversion system 1. FIG. FIG. 4 is a flow chart showing a first operation example of the power conversion system 1 . As shown in FIG. 3, the period from time t2 to time t6 is called an electric motor drive mode, the period from time t6 to time t8A is called transition mode 1, the period from time t8A to time t9 is called a voltage drop compensation mode, and time t9 to time t12. is called transition mode 2. Before time t1, the power conversion system 1, for example, the third switch 30 is closed and power is supplied to the load device 4, and the first switch 10, the second switch 20, the fourth switch 40 and the fifth The switch 50 is opened, the rotation speed of the electric motor 3 is 0, the inverter control unit 8 is in the gate block state, the changeover switches SW1a and SW1b are selected for the A terminal input, the switches SW3a and SW4b are in the open state, and the reference voltage circuit 821 is in the non-operating state. Description will be made with the holding state as the initial state. The initial state setting of the inverter control unit 8 before time t1 corresponds to step S100 in FIG. In the following description, the notation of each step in the flowchart is omitted (for example, step S100 is simply described as S100).

The switch control device 7 determines whether or not to start the electric motor 3 in S102. When it is determined to start the electric motor 3 (Yes in S102), the process proceeds to S104, and when it is determined not to start the electric motor 3 (No in S102), the process is continued.

When it is determined to start the electric motor 3 at time t1, the switch controller 7 advances to S104, closes the fifth switch 50, and supplies power from the AC power supply 2 to the power conversion device 6. At time t<b>2 , the switch control device 7 proceeds to S<b>106 to close the second switch 20 so that the power conversion device 6 can supply electric power to the electric motor 3 .

Next, at time t3, in S108, the inverter control unit 8 deblocks the gate, and the electric motor 3 starts a soft start to gradually increase the rotation speed.

In S110, the inverter control unit 8 determines whether or not the rotational speed ωr fed back from the electric motor 3 is greater than a predetermined set value (has reached the rated rotational speed). ), the process proceeds to S112, otherwise (No in S110), the process continues. At time t4, when the number of rotations of the electric motor 3 reaches the rated number of rotations, the inverter control unit 8 advances to S112 in order to perform synchronous operation of the electric motor 3, turns on the SW3a at time t4A, and slightly increases the frequency. is shifted from the frequency of the AC power supply 2 to perform phase adjustment (so-called uniform speed control).

Next, in S114, the inverter control section 8 determines whether or not the difference between the second power phase signal θs and the first reference phase signal θe is within a predetermined value. If the inverter control unit 8 determines that it is within the predetermined value (Yes in S114), it proceeds to the processing of S116, and if it determines that it is not within the predetermined value (No in S114), it continues the processing. At time t5, when the difference between the second power supply phase signal θs and the first reference phase signal θe becomes within a predetermined value, the inverter control section 8 proceeds to S116, via the switch control device 7, the first switch 10 is closed, the first switch 10 is closed, and when the first switch 10 is closed, power supply from the AC power supply 2 to the electric motor 3 is started. Furthermore, the switch SW3a is turned off.

Next, in S118, the switch control device 7 determines whether or not there is an energized current based on the answerback such as the auxiliary contact signal of the first switch 10 and the output of the first current detector 300. FIG. If the switch control device 7 determines that there is an answerback and an energized current (Yes in S118), it proceeds to the processing of S120. to continue. At time t6, when the switch control device 7 determines that there is an answerback and an energized current, the process advances to S120 to output an opening command for the second switch 20, the second switch 20 is opened, and the electric power is Power supply from the conversion device 6 to the electric motor 3 is stopped.

Then, at time t6A, the process proceeds to S122, and the inverter control section 8 switches the output selection of the changeover switches SW1a and SW2a from the A terminal input to the B terminal input. As a result, the voltage control signal, which is the input signal of the inverse d/q conversion section 83, is switched from the signal from the motor drive section 80 to the signal from the voltage sag compensation section. Furthermore, the first reference phase signal θe of the inverse d/q converter 83 is also switched from the signal based on the speed feedback from the motor drive unit 80 to the signal based on the phase of the AC power supply 2 . Therefore, the output voltage of the power converter 6 is controlled so as to follow the voltage and phase of the AC power supply 2 .

Proceeding to S126 at time t7, the switch control device 7 issues a closing command to close the fourth switch 40, the fourth switch 40 is closed, and the output of the power conversion device 6 is applied to the load device 4. 5.

Next, in S128, the switch control device 7 determines whether or not there is an answerback indicating that the fourth switch 40 is closed and an output current (conducting current) of the inverter circuit 62, and determines that there is. If yes (No in S128), the process proceeds to S130, and if not (No in S128), the process continues. At time t8, when it is determined that there is an output current from the inverter circuit 62 with the answer back, the process proceeds to S130, the switch controller 7 issues an open command to open the third switch 30, and the third switch 30 When opened, power is supplied to the load device 4 only from the power conversion device 6 .

At time t8A when the transient phenomenon of the AC power supply 2 due to the closing of the fourth switch 40 and the opening of the third switch ends and the voltage subsides, the process proceeds to S132, and the reference voltage circuit 821 keeps the output voltage constant at the value at time t8a. The power conversion system 1 operates in the voltage sag compensation mode. That is, in operation in the voltage sag compensation mode, the output voltage of the reference voltage circuit 821 is constant, so even if a voltage sag occurs in the AC power supply 2, the output voltage of the power converter 6 is kept constant and the load device 4 is supplied with stable power.

When the power conversion system 1 changes from the voltage sag compensation mode to the commercial power supply, at time t9, the reference voltage circuit 821 switches the value of the output voltage from holding to non-holding. As a result, the output voltage of the power converter 6 follows the voltage of the AC power supply 2 . At time t9A, SW4a is turned on to adjust the phase, and at time t9B, when the phase difference falls within a predetermined range, third switch 30 is closed and SW4a is turned off. Then, at time t10, when the answerback signal of the third switch 30 and the current are detected by the second current detector 400, the inverter circuit 62 is gate blocked, and the fourth switch 40 is opened. Then, at time t11, the outputs of the switches SW1a and SW2a are switched to select the A terminal input side. Then, at time t12, the second switch 20 is closed to enable power supply from the power conversion device 6 to the electric motor 3 .

After time t12, the motor drive mode is the same as that from time t2 to time t6, so the description is omitted.

In the case of a system in which the time to transition mode 2 after recovery from the voltage drop is sufficiently long compared to the pull-in time constant of the phase detection circuit PLL1A, at the start of transition mode 2, the first power supply phase signal θe2 and the second power supply phase signal θe2 Since the phase signals θs are substantially the same, SW4a may be omitted. Furthermore, the phase detection circuit PLL2A may be omitted and the first power phase signal θe2 may be used instead of the second power phase signal θs.

In S118 and S128, both the answerback signal and the energized current of each switch are checked, but one or both of them may be omitted if necessary.

Next, a second operation example of the power conversion system 1 will be described. FIG. 5 is a timing chart showing a second operation example of the power conversion system 1. FIG. In FIG. 5, the gate block and deblock timings of the inverter circuit 62 and the operation timings of the switches SW1a, SW2a and switches SW3a, SW4a are the same as in FIG. As shown in FIG. 5 , the power conversion system 1 starts the soft start of the electric motor 3 from a state where the third switch 30 is closed and power is supplied to the load device 4, for example.

First, the power conversion system 1 closes the fifth switch 50 at time t<b>1 ′ and closes the second switch 20 at time t<b>2 ′ to enable power supply to the electric motor 3 .

When the inverter control unit 8 of the power conversion system 1 deblocks the gate of the inverter circuit 62 at time t3', the electric motor 3 starts a soft start to gradually increase the rotation speed.

At time t4′, when the rotation speed of the electric motor 3 reaches the rated rotation speed, the power conversion system 1 performs speed uniform control in the same manner as in FIG. ', the first switch 10 is closed and power supply from the AC power supply 2 to the electric motor 3 is started.

Next, at time t6′, the power conversion system 1 closes the fourth switch 40 to connect the output of the power conversion device 6 to the load device 4, and at time t7′, the second switch 20 is opened to stop power supply from the power converter 6 to the electric motor 3 .

After that, at time t<b>8 ′, the power conversion system 1 opens the third switch 30 to enter the voltage drop compensation mode in which direct power supply from the AC power supply 2 to the load device 4 is stopped.

That is, in the second operation example of the power conversion system 1, the fourth switch 40 is closed while the second switch 20 remains closed. can be reduced.

As described above, the power conversion system 1 according to one embodiment can switch between the motor drive mode and the voltage sag compensation mode, and realizes soft start of the motor and voltage sag compensation for the load device with a simple configuration. can do.

In other words, the power conversion system 1 effectively utilizes the power conversion device 6 after the soft start of the electric motor 3, and even in the event of a momentary power failure in the system, it compensates for a momentary drop or momentary power failure without an uninterruptible power supply, and supplies power to electrical equipment. A stable supply can be achieved.

Some or all of the functions of the inverter control unit 8 may be included in the switch control device 7, and some or all of the functions of the switch control device 7 may be included in the inverter control unit 8. good. Furthermore, a storage battery or the like may be provided in parallel with the capacitor 61 of the DC circuit in order to lengthen the voltage sag compensation period. In addition, minor loop current control may be added to the voltage control of the momentary sag compensator 82, or feedback from the second voltage detector 200 to the reference voltage may be omitted and open loop control may be performed. Further, the reference voltage circuit 821 may be configured to be interlocked with the voltage sag detection circuit so as to hold the voltage immediately before the voltage sag occurs, and to enter the non-holding state after recovering from the voltage sag.

DESCRIPTION OF SYMBOLS 1... Power conversion system, 2... AC power supply, 3... Electric motor, 4... Load apparatus, 5... Transformer, 6... Power converter, 7... Switch control Apparatus 8... Inverter control unit 10... First switch 20... Second switch 30... Third switch 40... Fourth switch 50... Fifth Switch, 60... Converter Circuit, 61... Capacitor, 62... Inverter Circuit, 80... Electric Motor Drive Unit, 81... Phase Synchronization Unit, 82... Voltage Sag Compensation Unit, 83... inverse d/q conversion section, 84... PWM section, 100... first voltage detection section, 200... second voltage detection section, 300... first current detection section, 400. . . second current detector

Claims (5)

a power conversion device connected so as to be able to receive power from an AC power supply;
a second switch that connects or disconnects the output of the power conversion device to or from the electric motor;
a first switch that connects or disconnects the AC power supply to or from the electric motor;
a third switch that connects or disconnects the AC power supply to or from a load device;
a fourth switch that connects or disconnects the output of the power conversion device to or from the load device;
Equipped with a control unit,
The control unit supplies power from the power conversion device to the electric motor in a state in which the second switch and the third switch are closed and a state in which the first switch and the fourth switch are open, starting the electric motor, and after the electric motor reaches a predetermined speed, closing the first switch to connect the electric motor to the AC power supply so that the electric motor can receive power directly from the AC power supply; After that, the second switch is cut off, then the fourth switch is closed to supply power from the power conversion device to the load device, and then the third switch is cut off to turn off the power conversion. A power conversion system characterized by causing a device to perform a voltage sag compensation operation. a power conversion device connected so as to be able to receive power from an AC power supply;
a second switch that connects or disconnects the output of the power conversion device to or from the electric motor;
a first switch that connects or disconnects the AC power supply to or from the electric motor;
a third switch that connects or disconnects the AC power supply to or from a load device;
a fourth switch that connects or disconnects the output of the power conversion device to or from the load device;
Equipped with a control unit,
The control unit supplies power from the power conversion device to the electric motor in a state in which the second switch and the third switch are closed and a state in which the first switch and the fourth switch are open, starting the electric motor, and after the electric motor reaches a predetermined speed, closing the first switch to connect the electric motor to the AC power supply so that the electric motor can receive power directly from the AC power supply; After that, the fourth switch is closed to supply electric power from the power conversion device to the load device, and then the second switch and the third switch are cut off to operate the power conversion device for voltage sag compensation operation. A power conversion system characterized by: causing the power conversion device to perform a voltage sag compensation operation with the first switch, the second switch, and the third switch in an open state and the fourth switch in a closed state;
After closing the third switch, cut off the fourth switch and block the gate on the output side of the power converter,
After that, after closing the second switch, starting the electric motor in the power conversion device is started.
The power conversion system according to claim 1 or 2, characterized by : The control unit
a motor drive control unit that outputs signals for motor control of two orthogonal axes;
a momentary sag compensation control unit that outputs voltage control signals on two orthogonal axes;
an inverse d/q converter that generates a three-phase voltage control signal based on two orthogonal axis signal inputs and a reference phase signal;
a first phase detector that detects the phase of the output voltage of the power conversion device;
a second phase detector that detects the phase of the voltage of the AC power supply;
a first switching circuit for switching the orthogonal two-axis signal input of the inverse d/q conversion unit to the orthogonal two-axis motor control signal or the orthogonal two-axis voltage control signal;
a second switching circuit that switches the reference phase signal of the inverse d/q conversion unit to the output phase of the first phase detection unit or the output phase of the second phase detection unit;
The power conversion system according to any one of claims 1 to 3, comprising: The momentary sag compensation control unit includes a reference voltage circuit unit that serves as a reference for the two-axis voltage control signals,
In the non-holding state of the reference voltage circuit unit, the output of the reference voltage circuit unit follows the amplitude of the AC power supply,
In the hold state, the reference voltage circuit unit holds and outputs the output value of the reference voltage circuit unit that follows the amplitude of the AC power supply immediately before entering the previous hold state,
The reference voltage circuit unit enters a state of holding the reference voltage after the third switch is cut off,
The reference voltage is in a non-holding state after the third switch is cut off.
The power conversion system according to claim 4, characterized by :

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